Homer H. Clark was born around 1840 in Pomfret, New York, to John and Rebecca Clark. His father was a veteran of the War of 1812. The family moved to Raymond, Wisconsin, in the 1840s, and his father died there on September 1, 1848. By 1860, Clark was working as a mechanic in Milwaukee, Wisconsin.
He enlisted in the United States Army on September 7, 1861, and he mustered in as a sergeant in Company A of the 16th United States Infantry. According to his enlistment records, he was 5 feet, 11 ½ inches tall, with brown hair and gray eyes. He was promoted to 2nd lieutenant in November 1861 and to 1st lieutenant in February 1862. The regiment took part in the Peninsula campaign, the Second Battle of Manassas, the Battle of Antietam, the Battle of Fredericksburg, the Battle of Chancellorsville, the Battle of Gettysburg, and the Battle of Chickamauga.
Clark married Sophronia Macomber on October 22, 1862, and the couple had no children. He was wounded at Chickamauga on September 19, 1863, and he died of pyemia in Nashville, Tennessee, on October 20, 1863.