After the war, he served at Fort Adams, Rhode Island; against the Seminole Indians, 1849-50; and in garrison at Fort Adams again, 1851-53. For part of the next year, Steptoe was a member of a commission to evaluate whether there should be civil or military supervision of the national armories. He served the remainder of the year in garrison at Fort Wood, New York.
In the early summer of 1854, Steptoe was sent with a command of 175 soldiers and 150 civilian employees to Washington Territory to reconnoiter a military road to California and he was also sent to investigate the massacre of Captain John W. Gunnison and his party in Utah. Reaching Salt Lake City on 31 August, he chose to spend the winter with his troops in the Mormon capital while wintering his herd of 1,000 horses and mules in Rush Valley, south of Tooele, Utah.