Edward J. Steptoe was born in 1816. He was a native of Virginia, and later a United States Army officer, who graduated from the U.S. Military Academy on 1 July 1837. He served in the Indian conflicts in Florida from 1838 to 1842, including one assignment to help provide escort for the movement of the Cherokee west of the Mississippi River. From 1842 to 1846 Steptoe was stationed at the following posts: the U.S. Military Academy; Fort McHenry, Maryland; Savannah, Georgia; Fort Marion, Florida; and Fort Moultrie, South Carolina.
During the Mexican War, he was engaged in the Siege of Vera Cruz and, as a captain, fought in the battles of Cerro Gordo and San Antonio Garita. He was promoted to brevet major for gallant and meritorious conduct at Cerro Gordo, and to brevet lieutenant colonel as a result of his actions in the Battle of Chapultepec.