James G. Thomson was born November 12, 1778, the son of William Thomson and Margaret Popham. William Thomson was a tutor at the Newark Academy from 1780 to 1794, professor of languages and librarian at Dickinson College from 1794 until 1802, and professor of languages at Princeton from 1802 until 1828. Given his father’s position on the Dickinson faculty, it is not surprising that James G. Thomson earned his A.B. from Dickinson College in 1797.
In 1802 Thomson was made professor of Greek and Latin Languages at the University of Pennsylvania. In 1818 he was elected a member of the American Philosophical Society. Thomson married Mary, the daughter of Professor James Davidson, the last rector of the Academy of Philadelphia and then professor of Greek and Latin languages in the College. Mrs Thomson died in 1827; the couple had no children.
After resigning from his position on the University of Pennsylvania faculty, Thomson took up agriculture, principally at Hartsville, Pennsylvania. Several years before his death, Thomson moved to Frederickstown, Maryland, the residence of his brother John P. Thomson. James G. Thomson died there on June 18, 1847.