Confirming the Parentage of Theodore Higgins Arnold (c. 1798 – 1752)

I recently spent some time figuring out whether and how Theodore Higgins Arnold connects to my Arnold family.  Since it took a bit of digging, I figured I'd write it up to document my findings.

I came across Theodore Higgins Arnold in researching one of the distant branches of my Arnold family.  He is my second cousin, four times removed.  Multiple genealogies, both published and online, list Theodore Higgins Arnold as the eldest child of Freeman Arnold and his wife, Sarah ("Sally") Higgins.  I found documentation of Theodore Arnold's life, including his marriage and death, but could find no records to tie him his supposed parents.  There are lots of unsolved mysteries in the many branches of my Arnold family, but for various reasons this one piqued my interest.

Freeman and Sarah (Higgins) Arnold

Freeman Arnold (c. 1764 – 1846) married Sarah ("Sally") Higgins (c. 1775 – 1860) on April 23, 1797. The records of Haddam Neck Congregational Church list the baptisms of seven children of Freeman and Sally.

1. Sarah Arnold, born about 1801.
2. Freeman Arnold, born about 1805.
3. Justin Arnold, born about 1806.
4. Phebe Almira Arnold, born about 1811.
5. Samuel Higgins Arnold, born about 1813.
6. Martha Arnold, born about 1815.
7. Lyman Brooks Arnold, born 1817.

All of these children except for Sarah were baptized on October 3, 1819. Sarah was baptized on March 10, 1827. There is no record for a baptism of Theodore Higgins Arnold.

Theodore Higgins Arnold

My earliest information about Theodore Higgins Arnold records his marriage to Esther Selden on November 4, 1819, at the Haddam Neck Congregational Church in present-day East Hampton, Connecticut. He subsequently appears in the 1830, 1840, and 1850 U.S. Censuses for Haddam, Connecticut.  In all of these records he is listed as "Theodore H. Arnold." And the Haddam Neck Congregational Church recorded his admission and membership to that church in 1837 as "Theodore Higgins Arnold." 

Theodore Arnold died on September 24, 1852. His gravestone says he was 54 years old, which means he was born in 1797 or 1798.  This gravestone and other records from the time of his death refer to him as "Col. Theodore H. Arnold." I have not found anything that explains the title of Colonel, but I assume it is from the Connecticut militia as he is too young to have served in the Revolution or the War of 1812, and there is nothing to indicate that he spent a substantial amount of time in the regular Army.

I have found no records from his life time that name the parents of Theodore Higgins Arnold.

Connecting the dots (and the Arnolds)

This is the basic information I had when I started to consider whether Theodore Higgins Arnold was a child of Freeman and Sarah Arnold.  Superficially, the connection makes sense.

• Theodore Arnold's birthdate in 1797 or 1798 would fit nicely in the four year gap between the marriage of Freeman Arnold and Sarah Higgins in 1797 and the birth of their eldest daughter, Sarah, in about 1801.
• Theodore Higgins Arnold's middle name matches the maiden name of his supposed mother, Sarah Higgins.
• At first it seems odd that there are baptism records for the other children of Freeman and Sarah Arnold, but not for Theodore. But this is easily explained by the dates. The other children of Freeman and Sarah were baptized well after they were born. All except for the eldest daughter were baptized on October 13, 1819. At that point, Theodore Higgins Arnold would have been about 21 years old, and no longer a minor. So the decision whether to be baptized would have been up to him, not his parents. This likely explains why Freeman and Sarah Arnold's eldest daughter, Sarah, wasn't baptized at the same time as her younger siblings.

But I'm a natural skeptic. While these facts suggest that the connection is possible, they don't provide any proof.  So I went hunting for more information.

Eventually, I got curious about Theodore Higgins Arnold's name.  Suppose he was named for a relative named "Theodore Higgins." Could I find that relative? A few searches turned up a Theodore Higgins who died October 8, 1776. His death was listed in the records of the same Haddam Neck Congregational Church where Freeman and Sarah Arnold baptized their children 43 years later. And the probate of his estate provides the names of his widow, Phebe, his only son, Samuel, and his only daughter, "Salla."  Since Sarah Higgins was called "Sally" in many records, this is probably the same person.

As further evidence Theodore Higgins' only son, Samuel Higgins died in 1808. (He was a sea captain and died in the West Indies.) Freeman and Sarah (Higgins) Arnold had a son named Samuel Higgins Arnold born in about 1811. In fact, it appears that Freeman and Sarah named most of their children for close relatives. 

• Theodore Higgins Arnold, named for his maternal grandfather
• Sarah ("Sally") Arnold, named for her mother
• Freeman Arnold, named for his father
• Justin Arnold, likely named for his paternal grandfather (Jabez Arnold)
• Phebe Arnold, named for her maternal grandmother
• Samuel Higgins Arnold, named for his uncle
• Martha Arnold, named for her paternal grandmother

That leaves their youngest son, Lyman Brooks Arnold.  I wonder who he was named for.

The children of Theodore Higgins Arnold and Esther Selden

Household of Theodore H. Arnold as enumerated in the
1850 U.S. Census. 

Theodore H. Arnold (age 53) was enumerated in the 1850 U.S. Census for Haddam, Connecticut. Also in his household was his wife, Esther Arnold (age 50), and four potential children.

1. Ansel Arnold, age 27
2. Nelson Arnold, age 26
3. Wilson Arnold, age 21
4. Henry H. Arnold, age 14

Of course, the 1850 census doesn't tell us the relationships between the people in a household. In the 1840 census, five people were enumerated in the household of Theodore H. Arnold:

• 1 male age 40–49 (Theodore)
• 1 female age 40–49 (Esther)
• 2 males age 15–19 (Ansel & Nelson)
• 1 male age 10–14 (Wilson)

The three boys in the 1840 census correspond to the three oldest boys in the 1850 census (and they match in the 1830 census, as well). So it seems reasonable to infer that those boys (Ansel, Nelson, and Wilson) were sons of Theodore and Esther. But what about Henry H. Arnold? It could be that he is another son and was omitted (or was not at home) in the 1840 census. But I believe he was a cousin, rather than a child of Theodore and Esther. There was Henry H. Arnold of the right age who died in 1856.  His gravestone says that he was the son of Chauncey and Maria Arnold. Chauncey Arnold was a first cousin of Theodore Arnold and lived nearby. Chauncey's family was enumerated one page after Theodore's in the 1850 census.  And in that census, Chauncey Arnold's household does not include a Henry Arnold. 

Theodore Higgins and Esther (Selden) Arnold had at least one other child who wasn't captured in any of the censuses—Martha Arnold, who was born in about 1831 and died in 1834. It is possible they had one or more additional children who died young and were born between Nelson (c. 1824) and Wilson (c. 1829), but I haven't found any records of them.

There is also a nine year old girl, Cynthia E. Towner(?), who was enumerated in Theodore Arnold's household in 1850. She was enumerated with the family in 1860, as well. I have no idea who she is or what her connection to the family was.

Theodore Higgins Arnold is my 2nd cousin, four times removed. This diagram shows that relationship (the heavy lines), as well as the connections to other people in this post. Click on the image for a larger (and more readable) version.

Notes and Sources

The marriage of Freeman Arnold and Sarah Higgins was recorded in a list of marriages performed by Deacon Ezra Brainerd, Justice of the Peace and transcribed and posted by Jane Devlin.

The records of the Haddam Neck Congregational Church include the baptisms of all of Freeman and Sarah Arnold's children except Theodore Higgins Arnold, the marriage of Theodore Higgins Arnold, and the death of Theodore Higgins. I gathered this information from a set of abstracts of Connecticut church records:

Connecticut, Church Record Abstracts, 1630–1920, online index and images (Vol 027 East Hampton, 248 images, Arnolds on images 8–20, death of Theodore Higgins on image 124), Ancestry.com. Images from Connecticut, Church Records Index, Connecticut State Library, Hartford, Connecticut.

The death of Samuel Higgins was recorded in the records of the First Congregational Church of Haddam.

Connecticut, Church Record Abstracts, 1630–1920, online index and images (Vol 048 Haddam, image 162 of 331), Ancestry.com. Images from Connecticut, Church Records Index, Connecticut State Library, Hartford, Connecticut.

Theodore Higgins Arnold and his wife, Esther (Selden) Arnold are buried at Old Rock Landing Cemetery in Haddam, Connecticut. Images of their gravestones are available on Find A Grave, memorials 36049716 (Theodore) and 36051845 (Esther).

The distribution of Theodore Higgins estate, which lists "Salla" Higgins as his only daughter is part of Ancestry's enormous collection of Connecticut probate records:

Connecticut, Wills and Probate Records, 1609–1999, online index and images (Hartford, Probate Packets, Hickcox, J-Hubbard, Catherine, 1752–1880, images 704–722 of 1509), Ancestry.com, 

I found an image Henry H. Arnold's gravestone, listing his parents as Chauncey and Maria Arnold, on his Find A Grave memorial (#36052414).

Similarly, I identified Theodore Arnold's daughter, Martha Arnold, from her gravestone, also on Find A Grave (memorial #36054589). The gravestone identifies her parents as Theodore H. and Esther Arnold.

Disambiguating John Arnold of Hartford (1683 – 1741)

John Arnold's gravestone. "Here lies the Body of Serg'nt
John Arnold who Died November the 30th A.D. 1741
Aged 58 years." Photograph by Jim Bancroft, originally
posted to John Arnold's Find A Grave page.

John Arnold died on November 30, 1741 and was buried at Center Cemetery in East Hartford, Connecticut.  His gravestone, shown here, says he was 58 years old at his death.  Simple arithmetic tells us therefore that he was born in 1683 or 1684.  Nevertheless, there are countless online trees that say he was born more than twenty years earlier, in 1662, 1663, or 1664. Similarly, his birthdate in FamilySearch's family tree has been edited multiple times, switching between 1683 and these other dates.

So what's going on here?  The short version is that there was a second John Arnold who was born in about 1663, and researchers have conflated these two people.

In this post, I will explain this in more detail, first by laying out the facts I know about John Arnold, then describing how I think this error originated, and providing enough information about the two John Arnolds to make it clear that they can't be the same person.

Obviously this is good fodder for a blog post. If I can also save other researchers some confusion, all the better!

John Arnold of Hartford

Working backwards from his gravestone, I pieced together some basic information about John Arnold. His will, dated November 14, 1741, provided a starting point. It gave me the name of his wife, Hannah; two sons, John and Henry; three married daughters, Hannah, Mary, and Sarah; and his deceased brother, Henry Arnold. Early Hartford records provided the birth dates for all five of these children along with a third son, Samuel, who died in 1739. The children were born between 1710 and 1722. Earlier than that, the marriage of John Arnold and Hannah Meakins was recorded on January 12, 1709/10.

The fact that John Arnold had a brother, Henry, who predeceased him turned out to be a particularly useful piece of information, and helped me find his parents. Hartford probate records include the will of a Henry Arnold who had two sons, Henry and John. They also have records for the probate of Henry Arnold Jr.  Both estates were probated on the same date, and in both cases administration was granted to John Arnold. Since these facts agree with the information from John Arnold's will, it seems likely that this his family.

The following graphic shows the family of John Arnold based on the information from these records.

The family of John Arnold of Hartford. John Arnold is shown with a heavy outline, along with his parents,
siblings, wife, and children.

Confusion about John Arnold's Birth

I have found no records of John Arnold's life prior to his marriage. So his gravestone is my only evidence of when he was born.  But many other researchers think he was born in the 1660s. Where are they getting their dates from? The confusion seems to come from another John Arnold, who lived in Haddam, about 25 miles south of Hartford on the Connecticut River. 

List of the children of Joseph Arnold with their ages.
From the probate records for Joseph Arnold. Elsewhere on
the page it is labeled, "Jos Arnolds Inventory July 1692."

One of the few records that mentions John Arnold of Haddam is the probate of his father's estate. His father, Joseph Arnold, died intestate on October 22, 1691. On the back of his estate inventory is a list of his children and their ages.  First on the list is "John Arnold 29 years old."  The inventory is dated "July 1692."  So assuming that Joseph's son Arnold was 29 years old in 1692, that would put his birth in 1662 or 1663, matching the mysterious birthdate sometimes associated with John Arnold of Hartford.

Could these two John Arnolds, in fact, be the same person? Perhaps the age on the East Hartford gravestone is wrong. But this seems impossible since the two John Arnolds have different fathers. The father of John Arnold of Hartford was Henry Arnold, and the father of John Arnold of Haddam was Joseph Arnold. Nevertheless, the confusion is understandable, especially if you don't have all of this information.

As an added twist, some of the trees that say John Arnold of Hartford was born in 1662 cite a family bible as a source.  I was curious to see what information was in bible and tracked it down at the Connecticut State Library, paying a few dollars to have it scanned and emailed to me.

The bible itself is an American Bible Society edition printed in 1849. On the family record pages are the births, deaths, and marriages of dozens of people. These names are mostly Arnolds, and the dates are primarily from the 1800s, including some as late as 1890. John Arnold of Hartford is among the earliest names listed in it, The dates for his death and birth match those from his gravestone. Included with the bible are about twenty pages of genealogical writing about the same names that are listed in the bible. This document describes the John Arnold's gravestone in East Hartford. Its author also speculates that the father of John Arnold was Joseph Arnold. ("I think this John to have been the son of that Joseph who...")

Based on this information, I conclude two things about the bible record and the associated notes. First, it was written in the mid-1800s, a century after the lifetime of John Arnold of Hartford. So the information about John Arnold is not first hand knowledge. Second, the owner of this bible didn't have access to any source I haven't already found, and likely had less information. In particular, it seems reasonable to conclude he or she hadn't found the wills and probate records I've described, as those would have refuted the theory that Joseph Arnold of Haddam was the father of John Arnold of Hartford.

Conclusion

There are no surprising conclusions here. But I hope that by spelling out what I have discovered about John Arnold of Hartford (and his namesake in Haddam), I can dispel some of the misinformation about his birth. If nothing else, this will give me something to refer to the next time I have to correct John Arnold's birthdate on FamilySearch.

Notes and Sources

I have not seen the original Hartford records that provide information about the marriage and children of John Arnold of Hartford, but they have been copied and indexed in many places. The marriage of John Arnold and Hannah Meakins appears in:

"Hartford Records," transcribed by Lucius M. Boltwood, New England Historical and Genealogical Register (NEHGR), vol. 13, p. 141, April 1859.

The births of their children are in the Barbour Collection of Connecticut Town Vital Records:

Ancestry.com, "Connecticut Town Birth Records, pre-1870 (Barbour Collection)," Hartford Vital Records 1635–1855, image 9 of 467.

Since the Barbour Collection included a record for the birth of Samuel Arnold in 1720, but Samuel wasn't mentioned in John Arnold's will, I inferred that he had died before the will was written. This was confirmed by finding his gravestone on Find A Grave, showing that he died on November 19, 1739. The genealogical notes in the John Arnold family bible (see below) states that this stone is nearby that of John Arnold.

The wills and probate records related to the two John Arnolds can be found in Charles Manwaring's Digest of Early Connecticut Probate Records.

John Arnold of Hartford:

Charles William Manwaring (ed.), A Digest of the Early Connecticut Probate Records, Vol III, Hartford District, 1729–1750 (R.S. Peck & Co., Hartford, Conn., 1906), p. 381.

Henry Arnold (father of John Arnold of Hartford):

Charles William Manwaring (ed.), A Digest of the Early Connecticut Probate Records, Vol II, Hartford District, 1700–1729 (R.S. Peck & Co., Hartford, Conn., 1904), pp. 459–460.

Henry Arnold Jr. (brother of John Arnold of Hartford):

Charles William Manwaring (ed.), A Digest of the Early Connecticut Probate Records, Vol II, Hartford District, 1700–1729 (R.S. Peck & Co., Hartford, Conn., 1904), pp. 460–461.

Joseph Arnold (father of John Arnold of Haddam):

Charles William Manwaring (ed.), A Digest of the Early Connecticut Probate Records, Vol I, Hartford District, 1635–1700 (R.S. Peck & Co., Hartford, Conn., 1904), p. 401.

The Manwaring transcription of Joseph Arnold's probate includes the list of Joseph Arnold's children and their ages. But it is not clear about the date of the document it is attached to.  Images of the original probate records are available from Ancestry's Connecticut Wills and Probate Records collection. The last page of this record includes the list of ages, excerpted above. Elsewhere on this page is written, "Jos Arnolds Inventory July 1692."

Connecticut, Wills and Probate Records, 1609–1999, online index and images, Ancestry.com, Hartford Probate district > Probate Packets > Antrim–Ayrault > M, 1641–1880 > images 417–423 of 1517.

Finally there is the John Arnold bible record:

"John Arnold of Hartford," Bible & Family Records, Vol 25, pp. 35–56, Connecticut State Library, Hartford, Connecticut. 

A slave owner in my family

An excerpt from the will of Samuel Arnold of East Haddam, Connecticut, "Imprimis, I give and bequeath unto my Beloved wife Abigal one third part of my movable Estate (excepting my negro slaves) to her, her heirs and assigns forever..."

If you had asked me a year ago whether any of my ancestors owned slaves, I would have said, "I doubt it."  Before the Civil War, all of my American ancestors lived in New England and New York. I know that slavery existed in those parts of the country as well as in the South. But there were far fewer enslaved people in the North.  So what were the odds that one of my ancestors would own slaves?

Then I found my 7th great-uncle, Samuel Arnold of East Haddam, Connecticut. Or, to be more precise, I discovered his will. In that will (excerpted above), Samuel Arnold named nine different "negro slaves," and specified which of them he was leaving to each of his children. So I certainly have at least one relative who owned slaves, or more if we count his heirs.

Samuel Arnold was my 7th grand uncle

I always find wills and probate records interesting. This one is particularly interesting since it is from a time (1739), when it is rare to find any information about a relative other than the basic vital statistics about their birth, marriage, death, and children.

Obviously, what jumped out at me about Samuel Arnold's will was the slaves. But as often happens, a little bit of information leads to even more questions. The will describes relationships among a few of the slaves, (e.g., "Prince, ye 5th son of my eldest man servant named Prince and of Cate his wife.") Were the other slaves also related to Prince and Cate? Since Prince was their fifth son, they had at least four other sons, and the will names exactly four other male slaves—Sampson, Ceaser [sic], Japhet, and Peter. Were they the older sons of Prince and Cate? The other named slaves are Lois and Rose. Were they then the daughters of Prince and Cate?

I also wonder what happened to these enslaved people after Samuel Arnold's death. His will distributes them among his seven children. But the inventory of his estate does not include the slaves! The will is dated November 3, 1738, Samuel Arnold died on March 30, 1739, and the inventory was taken April 27, 1739. Did Samuel Arnold sell his slaves between those dates? Did he free them? Or did he give the slaves to his children prior to his death? And other than Samuel Arnold's will I have found no information about Prince and Cate and their family. A few later probate records mention slaves with the same names. For example the will of John Stocking of Middletown, Connecticut, dated December 2, 1746, leaves his "negro girl Rose" to his mother. But there is no way to tell if this is the same Rose that Samuel Arnold left to his son Josiah.

I am also curious about the younger slave named Prince.  Most of the bequests in Samuel Arnold's will are quite simple. (E.g., "I give unto my son Enoch Arnold... my negro man servant called Ceaser.") But he leaves much more elaborate instructions about Prince:

"I give to my son Samuel Arnold... my negro man servant named Prince, ye 5th son of my eldest man servant named Prince and of Cate his wife, and also my will is that the aforesaid servant shall at my decease be in the hands of my executors and by them to be put in the hands of my son Samuel if they shall judge it best for him to have the sd. servant; but if my sd. executors shall judge it best to sell the sd. servant and my sd. son to have ye money, then my will is that my executors shall sell my sd. servant in the following manner, viz.: to such suitable master as will give most for my sd. servant, and to pay £10 a year annually until the payment be out; and also my will is that my sd. son shall have the money according to the foregoing proposal of payment, provided my sd. servant shall not be sold to any master living out of this town."

Why was Prince singled out to be "in the hands of" Samuel Arnold's executors at his decease? Why might those executors judge it best to sell Prince rather than leave him to the younger Samuel Arnold? Does this reflect something about Prince or the younger Samuel? The latter was not a juvenile. He graduated from Yale College in 1724 and was likely in his 30s when his father wrote this will.

Samuel Arnold was a distant uncle. I don't know if any of my direct ancestors also owned slaves. Since Samuel Arnold did, it seems possible his close relatives did as well. The likely candidates on my Arnold line would be Joseph Arnold (my 7th great-grandfather and Samuel's father), John Arnold (my 6th great-grandfather and Samuel's brother) or Gideon Arnold (my 5th great grandfather and Samuel's nephew).  They all lived in Haddam, Connecticut, across the Connecticut River from East Haddam, where Samuel settled. Joseph Arnold died intestate in 1691; the inventory of his estate does not include any slaves. I have not (yet?) found any probate records for John or Gideon Arnold. So for the time being, this question remains a mystery.

In the absence of concrete information about my direct ancestors, I decided to read up a little on slavery in early Connecticut. How typical (or not) was Samuel Arnold? Were there many enslaved people in Haddam and East Haddam? Who owned slaves in colonial Connecticut and why? Did slavery contribute to the economy?  I.e., did enslaved people increase production enough to balance out the costs of feeding and supporting them, and if so were they a less expensive source of labor than free laborers?  Or was owning slaves a novelty or status symbol? And how did Connecticut transition from allowing slavery in the mid-18th century to being a free state a century later on the eve of the Civil War?

Samuel Arnold's estate was valued at £441, making him well-off, but not among the wealthy elite of Connecticut. This makes his situation rather unusual. In a survey of estate inventories from eighteenth century Connecticut, only 3% of estates valued at less than £500 included slaves. And those estates typically included only one or two slaves. So Samuel Arnold was among that 3% and was something of a rarity in having nine slaves.

While some farmers, like Samuel Arnold, owned slaves, the use of enslaved labor was more common among craftsmen, merchants, and the wealthy.  Large-scale farmers and artisans might have had economic motives for using enslaved labor, needing a full-time worker to perform a particularly arduous or dangerous job. But it appears that many slaves were used for menial chores or as valets and maids, suggesting that a large portion of enslaved labor did not contribute to the economy.

In the early part of the eighteenth century, there was little moral objection to slavery. It was common for ministers in Connecticut to own slaves, just as it was for doctors, military officers, and other successful professionals. While this attitude was shared throughout the early colonies, it seems slavery was more popular in Connecticut than in its neighbors. As a result, Connecticut was relatively slow in eliminating the practice.

The 1790 census enumerated 2,764 slaves in Connecticut, accounting for 1.16% of the population. While this was more slaves than the combined total for the rest of the New England states, it was also quite small compared to the southern states; South Carolina had 107,094 slaves, representing 43% of its population.

By 1790, Connecticut had already started on the road to abolition. In 1784, the legislature enacted gradual emancipation, freeing all enslaved people when they reached age 25. A 1797 law lowered this age to 21. These laws meant that slavery would slowly decline in Connecticut, but they also condemned those where were enslaved and over 25 to live out their lives in servitude.

Connecticut did not officially outlaw slavery until 1848, making it the last New England state to do so.  But by that time gradual emancipation had greatly reduced the enslaved population. In 1840, there were only 54 slaves in Connecticut.


Notes on Sources

I originally found Samuel Arnold's will in Manwaring's collection of Connecticut Probate records:

Charles William Manwaring (ed.), A Digest of the Early Connecticut Probate Records, Vol III, Hartford District, 1729–1750 (R.S. Peck & Co., Hartford, Conn., 1906), pp. 219–220. 

This three volume set was my first foray into estate records, and contains probate records for many of my ancestors Hartford and Haddam Connecticut. All three volumes are available and searchable at archive.org. John Stocking's will is on pages 660–661 of the third volume.

I subsequently found the images of the original probate papers when Ancestry.com introduced their massive collection of Connecticut Wills and Probate Records. In addition to providing the text from the will pictured at the top of the page, this also provided a copy of Samuel Arnold's estate inventory.

Connecticut, Wills and Probate Records, 1609–1999, online index and images, Ancestry.com, Hartford Probate district: Probate Packets, Antrim-Ayrault, M, 1641–1880: images 529–541 of 1517; 

The dates of Samuel Arnold's will and estate inventory are from his probate records. I found the date of his death in the Barbour Collection of Connecticut Town Records.

Connecticut Town Death Records, pre-1870 (Barbour Collection), online index and images, Ancestry.com, East Haddam Vital Records 1743–1857: image 14 of 258.

A brief biography of the younger Samuel Arnold appears in a collection of biographical sketches of early graduates of Yale College. It states that he was baptized on October 8, 1704 in East Haddam, making him at least 34 years old when his father's will was written.

Franklin Bowditch Dexter, Biographical Sketches of the Graduates of Yale College with Annals of the College History, October, 1701—May, 1745 (Henry Holt and Company, New York, 1885), pp. 292–3. Available via Archive.org.

Statistics about eighteenth century slavery in Connecticut were taken from:

Jackson Turner Main, Society and Economy in Colonial Connecticut (Princeton University Press, Princeton, NJ, 1985).

This book presents a fascinating picture of many aspects of colonial life in Connecticut. The author collected information from estate inventories from all parts of Connecticut. Using this information, he analyzed many aspects of economic and material life in the colony. The statistics about slavery are just a small part of this work. Given the methodology, it seemed fitting to use this book in researching a question triggered by Samuel Arnold's own will and estate inventory.

Data on the enumeration of slaves in the 1790 census was provided by the Wikipedia article on that census.

The Connecticut History web site provides an excellent overview of gradual emancipation.