Polly Williams

Yes. I can identify the missing branch as Polly Williams, wife of Thaddeus Rockwell (1782–1874) in the tree you showed. I dug into the Ohio/New York evidence, and there is an important distinction between what is documented and what is merely appearing in online family trees.

What I can establish

Your Polly is the woman who:

• Polly Williams

• born about 1785/1786

• died September 6, 1841

• married Thaddeus Rockwell

• was living in New York before coming to Greenfield Township, Huron County, Ohio

• was the mother of Polly Rockwell, born August 1, 1820 at Taylor, New York

The Ohio cemetery transcription is particularly useful: it records “Polly, w/o Thaddeus Rockwell,” died Sept. 6, 1841, age 55, giving a birth date around 1786.

Even better, the Huron County historical record identifies your later Polly Rockwell as the daughter of Thaddeus Rockwell, born at Taylor, New York, August 1, 1820, and says she came with her parents to Greenfield Township in 1836.

And the Huron County Pioneer Ladies database explicitly gives:

Polly Rockwell — married Hiram Smith — parents Thaddeus Rockwell / Polly — birthplace Taylor, NY.

But I have NOT yet found her parents

This is the important part: I don’t think we should put a father and mother into your tree yet simply from an online-tree match.

I searched specifically for:

Polly Williams, c.1785/86–1841 + Thaddeus Rockwell

and did not find a sufficiently reliable record naming her parents.

There are many Polly Williams born around this period, and several are demonstrably different women. For example, the genealogical databases return Polly Williams with entirely different parents and locations, so attaching one merely because the dates are close would be dangerous.

There is another very important clue

The large Genealogy of the Families of John Rockwell of Stamford does document a different Thaddeus Rockwell, born March 10, 1782, son of Thomas Rockwell and Ruth Benedict, who died at Ridgefield in 1834 and married Abiah Nash.

That is not your Thaddeus if your tree’s 1782–1874 dates are correct.

So I would not currently fill Polly’s parents by assuming that her husband Thaddeus was the son of Thomas Rockwell and Ruth Benedict. That’s exactly the kind of tempting same-name connection that can corrupt a genealogy.

Your tree should currently look like this

             ? WILLIAMS

                  │

                  ├── Polly Williams

                  │   c.1785/86 – 6 Sep 1841

                  │        │

                  │        │ married

                  │        ▼

                  │   Thaddeus Rockwell

                  │   1782 – 1874

                  │        │

                  │        └── Polly Rockwell

                  │            1 Aug 1820 – 1904

                  │                 │

                  │                 └── Hiram Smith

                  │

So the two boxes immediately above Polly Williams should remain blank for now.

What I think is the best next research target

We now have an unusually good geographic trail:

Polly Williams + Thaddeus Rockwell → Taylor, New York → Greenfield Township, Ohio

and we know Polly Williams died in Greenfield in 1841.

The next records I’d pursue are:

1. Taylor/Cortland County NY church records around 1810–1820

2. Thaddeus Rockwell’s New York land deeds

3. 1810, 1820 and 1830 census records

4. Thaddeus’s probate/estate

5. Polly’s 1841 estate or guardianship records

6. Marriage record for Thaddeus Rockwell + Polly Williams

7. Other children of Thaddeus and Polly — a sibling’s record may name Polly’s maiden-family connection.

That last one could be the breakthrough.

So I would not add guessed parents to your tree yet. We have positively established that the missing wife is Polly Williams, born about 1786 and died September 6, 1841, but her parents remain an unresolved genealogical question based on the records I could verify.

If you want, the next thing I’d work on is  the 1810–1830 New York census/deed trail for Thaddeus Rockwell and Polly, because that has the best chance of actually exposing  Polly Williams’s father and mother rather than giving you another speculative online-tree connection.