He is listed in the US Census of 1880 (LDS/Family Search - free site):
J.S.Simonton b. PA born 1829 - single age 51 Prof. in College Parents b. PA
Living with:Sarah Hanna b. 1803 age 77 widow - boarding house.
location:4th Ward, Washington, Washington Co, PA
James Snodgrass Simonton is his full name.He is part of the Simonton family that went to Brazil as Presbyterian missionaries.His brother Ashbel Green Simonton and his sister (married Rev. Blackford) went there as well.
Later James Snodgrass Simonton married Jane Lemoyne of Washington, PA
James Simonton is listed in the 1850 and 1870 US Census in Dauphin County and Washington Co, PA on Ancestry.com