After studying law, he was admitted to the bar in 1862 and commenced practice in
Edwardsville, Illinois. He enlisted in the
Union Army on August 12, 1862. He was promoted to second lieutenant, Company G,
117th Illinois Volunteer Infantry Regiment, in 1863 and to first lieutenant in 1864. He served as member of the
Illinois House of Representatives in 1868, serving until 1870. In 1870 he moved to
Grundy Center, Iowa, where he continued to practice law, and also farmed. Kerr was elected as a Republican to the
50th United States Congress, unseating incumbent Democrat
Benjamin T. Frederick. After re-election in 1888 and service in the
Fifty-first Congress, he declined to run for a third term in 1890. In all, he served in Congress from March 4, 1887, to March 3, 1891. After leaving Congress, Kerr resumed the practice of law. Kerr had served as a delegate to the Republican National Convention in 1888 and 1896. In 1896 he indicated that he supported the free coinage of silver, a position closer to Democratic presidential candidate
William Jennings Bryan than to his own party's candidate,
William McKinley. Soon thereafter he switched parties, becoming a Democrat. He was an unsuccessful Democratic candidate for election in 1900 to his former seat in Congress. == Personal life ==