Born at
Orange Court House, Virginia, Jenkins entered the Navy as a
midshipman on 1 November 1828, and served first in the
West Indies in an expedition against pirates and slavers. Examined for a commission as lieutenant, he placed first among 82 candidates. In 1831 Jenkins helped to suppress
Nat Turner's slave rebellion. Prior to the
Mexican–American War, Jenkins served with the
United States Coast Survey and with the Brazilian and Mediterranean Squadrons. During the war with
Mexico, as executive officer of , he led landing parties from his ship at
Tuxpan and
Tabasco. Later, he commanded the store-ship and the supply station at
Salmedina Island. In the interval between the wars, he served in the
receiving ship at
Baltimore,
Maryland, returned to the U.S. Coast Survey, and was secretary of the
Lighthouse Board. Jenkins was promoted to commander on 14 September 1855. From September 1858 to October 1860, he commanded the sloop-of-war on
Brazil Station and in the Gulf of Mexico. His ship participated in the
Paraguay expedition. ==Civil War service==