Biography of John William Thompson, of Poweshiek, Iowa, reads in part: "His great-grandfather [grandfather makes more sense] Thompson was born in 1776, in Ireland, where he was educated and where he followed farming until his eighteenth year, when he sailed for America, and settled in Belmont county, Ohio, where he taught school. Here he married Jane Lundy, who bore him six children, one of whom was John, born June 3, 1802. He was a farmer; married, January 31, 1828, Sarah McWilliams, who was born October 17, 1805, in Fayette, Pennsylvania. Her grandfather Samuel came from Ireland at an early day and settled in Pennsylvania. Her husband died February 13, 1854, and she, a pleasant and kindly old lady, lives with her son John William, the subject of this biography, who was born February 3, 1845, in Belmont county, Ohio, where he was raised and educated. 
One of the unsourced family trees on Ancestry identifies his grandfather as Samuel Thompson, buried in Belmont County, Ohio  and his grandmother as Ann Jane Lundy Thompson, 1780-1818. According to the Find a Grave site, Samuel Thompson's wife was Elizabeth (Hogue) Baggs Matlock married on January 7th, 1819 in Belmont County, Ohio. This marriage date conforms to the assumption that Jane Lundy was his first wife and that Jane died in 1818.
The Ancestry site also tries to link Samuel Thompson as a son of Jacob Thompson and Ann Downard, the ancestors of Sarah Frame McWilliams Thompson. The six children are incorrect and the birth dates of some come after their parents' death dates.
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