John Mansfield (August 1822 – May 6, 1896) was the 15th Lieutenant Governor of California from 1880 to 1883. He also was an officer in the Union Army during the American Civil War. Originally from Monroe County, New York, Mansfield emigrated to Wisconsin prior to the Civil War.Following President Abraham Lincoln's call for 75,000 state militia troops in April 1861 to suppress the Confederate rebellion, Mansfield was commissioned as captain of Company G, 2nd Wisconsin Volunteer Infantry Regiment, known as the "Portage Guards." Mustered at Camp Randall on June 11, 1861, Mansfield's regiment entered as a three-year regiment and departed Madison for Washington, D.C. on June 20 to join the Army of the Potomac. At Washington, Mansfield's regiment was brigaded under William T. Sherman along with the 13th New York Volunteer Infantry, the 69th New York Volunteer Infantry and the 79th New York Volunteer Infantry.Mansfield's regiment first saw action at the First Battle of Bull Run. He served at many of the important battles of the Army of the Potomac, including the battles of South Mountain, Antietam, and Gettysburg, where, as the regiment's major, he assumed command of the 2nd Wisconsin after the senior officer, Lucius Fairchild, was shot. He was subsequently promoted to lieutenant colonel and served in the Bristoe and Mine Run Campaigns. As Colonel of the 2nd Wisconsin, he was wounded and captured in May or June 1864 during the Overland Campaign.Towards the end of the Civil War, Mansfield became colonel of the 12th Veteran Reserve Corps, a regiment of former soldiers who had reenlisted. In the omnibus promotions in 1866 following the cessation of hostilities, he was brevetted as a brigadier general of volunteers for "gallant and meritorious services during the war," a rank to date from March 13, 1865. Mansfield moved to California after resigning from the army and was a delegate to the 1880 Republican National Convention. He served as Lieutenant Governor under George C. Perkins for the next three years as a Republican. Mansfield died in Los Angeles and was cremated. His ashes are interred in Angelus-Rosedale Cemetery in an unmarked grave. He is the namesake of Mansfield, Illinois.