He became involved in California politics and from 1859 to 1860 he was Secretary of State of California, during the administration of Governor John B. Weller. Following the beginning of the Civil War, he joined the 4th Regiment of California Infantry as lieutenant Colonel but became colonel commanding the 4th Regiment from November, 1861 succeeding Colonel Henry M. Judah in command of the regiment. His regimental headquarters and several companies were sent from San Francisco to Camp Latham in Southern California in late 1861. On May 2, 1862, General George Wright wrote to Colonel Ferris Foreman, the new commander of Camp Latham to send, two or three companies of the Second Cavalry with Lieutenant Colonel George S. Evans as commander to establish a post in the Owens Valley. He was Commander of the District of Southern California from May 15, 1862, to May 17, 1862, and from April 10, 1863, to July 7, 1863. Colonel Foreman commanded the 4th Regiment until August 20, 1863, when he resigned. Shortly afterward, Foreman's daughter Ann was discovered to have been in communication with the infamous secessionist and duelist Daniel Showalter who wrote her an affectionate letter that was found on the body of a Confederate spy in west Texas in September 1863. With the Republicans dominating California politics, Foreman returned to Illinois and became the Fayette County State's Attorney and was a delegate to the Illinois state constitutional convention for the 13th District in 1870. He returned to California in his later years, and died in Stockton, San Joaquin County, February 11, 1901. He was buried at San Joaquin Catholic Cemetery, in Stockton.