Stephen Gardner Champlin was born July 1st 1827 in Kingston, New York, the son of Jeffrey Clark and Allis Ellen Champlin. He attended local academies and then began studying medicine. In 1845 Champlin had a medical practice in Warwarsing, Ulster, New York. He decided in 1849 to become a lawyer and attended a law school in Balston Spa, New York. He was admitted to the New York State bar and opened a practice in Albany, New York. Champlin moved to Grand Rapids, Michigan in 1853 where he opened a law practice with Lucius Patterson. Champlin joined the Michigan state militia and was elected the Captain of the Grand Rapids Light Artillery. In the fall of 1858 Champlin was elected the Prosecuting Attorney of Kent County, Michigan.
Champlin entered the Union Army June 10th 1861 as a Major in the 3rd Michigan Infantry. Their first action was a reconnaissance near Bailey’s Corners in Virginia on August 30th 1861 for which Union Major General George B McClellan said of Champlin, I am “pleased with Major Champlin's dispositions on the occasion”. Champlin was promoted to Colonel of the 3rd Michigan October 28th 1861. He was wounded in the hip at the Battle of Seven Pines. After partially recovering Champlin led the regiment at the Second Battle of Bull Run, and was again wounded. While recovering from both wounds in Washington, DC, Champlin was promoted on November 29th 1862, to Brigadier General.
Champlin was placed in command of the Draft Depot at Camp Cleveland, Ohio in 1863. He was then re-assigned on September 22nd 1863 to the Draft Depot in Grand Rapids, Michigan. Champlin’s wounds did not heal well, and on November 8th 1863 he resigned his commission. He died January 24th 1864 at his home as a result of complications of his wounds and is buried in the Fulton Street Cemetery in Grand Rapids, Michigan.