For the record, here’s one more source to add to our list of “not Jonathan M. Clark’s kin” dead ends in the search for JMC’s roots in northern Vermont and Lower Canada, circa 1800-1840.

Clark, Almon W., 1541-1907. The Clark family genealogy in the United States, a genealogical record showing sources of the English ancestors. Stamford, N.Y., Press of the Mirror-recorder, 1907. Library of Congress
What’s here, what’s not?
I did not read through every page of this volume, but I downloaded a PDF copy from the Library of Congress, skimmed through some of the introductory material and then ran a series of searches for various key words. I had no hits, or few relevant hits, on keywords: STANSTEAD, CANADA, QUEBEC (also P.Q.), WISCONSIN (also WIS), RIX, MORRILL and MERRILL, VERMONT (also VT), HAMPSHIRE (also HAMP and N.H.), DERBY and MILWAUKEE.
The book begins with a profile of one “Randall Clark, the pioneer of the Clark family, of Blenheim Hill, [who] was born in Charleston, R. I., Oct. 28, 1 788.” This family appears to have deep roots in southern New England and subsequently in New York state and much of the genealogical information here is focused on Clark descendants in mid- to late-nineteenth century New York. It looks like a few branches of the family moved to Illinois in the mid-1800s, but not Wisconsin.
So if your Clark family research has a strong Rhode Island, Massachusetts, Connecticut or New York state component, you may find this book useful. But in our search for JMC’s kin in Vermont, New Hampshire and Lower Canada, this book goes on the “Nope” shelf.