Atwater graduated from Hobart College in Geneva, New York, and became a lawyer. He went west with his uncle to St. Louis, and then settled in Putnam County in 1834. He made his home in Hennepin, where he also opened a legal practice. Atwater represented Putnam County in the Illinois House of Representatives in the Tenth General Assembly. In 1847, Atwater lost his election bid to be Putnam County's delegate at the Illinois State Constitutional Convention. He was a practicing lawyer, a justice of the peace, and a county court judge.
Francis Atwater, comp., Atwater History and Genealogy, 4 vols. (Meriden, CT: Horton Printing, 1927), 4:124; John Spencer Burt and W. E. Hawthorne, Past and Present of Marshall and Putnam Counties, Illinois (Chicago: Pioneer, 1907), 83, 88.