In 1856 he helped organize the Republican party in Iowa. At the convention in Iowa City, Grinnell was instrumental in "the delicate task" of bringing together abolitionists, temperance advocates, Know Nothings, and former Whigs. He won election to the state senate in 1856 and 1858 on the platform of temperance, free public education for all, and free soil. He tirelessly argued that not only were such positions morally correct, but they would bring prosperity by increasing the value of labor and the land.

GRINNELL, Josiah Bushnell, a Representative from Iowa; born in New Haven, Addison County, Vt., December 22, 1821; attended the common schools and Oneida Institute; pursued classical studies; was graduated from Auburn Theological Seminary in 1847; ordained a Presbyterian clergyman; held pastorates in Union Village, N.Y., Washington, D.C., and in the Congregational Church of New York City; moved to Iowa in 1854 and founded the town of Grinnell, Poweshiek County, and also Grinnell University; member of the State senate 1856-1860; studied law; was admitted to the bar in 1858