American Civil War Jacob Zeilin (July 16, 1806 – November 18, 1880) was the United States Marine Corps' first non-brevet flag officer.

He attended the United States Military Academy from 1822 to 1825,[2] but dropped out due to poor grades in philosophy and chemistry.

He first went to sea on board the sloop of war Erie in March 1832, which was followed by a tour of duty at Charlestown (Boston), Massachusetts.

In February 1842, he returned to sea duty, on board the USS Columbus, and during the cruise that followed spent several months on the Brazil station.

During the Mexican–American War, Zeilin commanded the Marine Detachment embarked in Congress, which ship was attached to Commodore Robert F. Stockton's force.

[4] On 28 January 1847, Zeilin was appointed Military Commandant of San Diego and served in that capacity until the completion of the conquest of California.

[1] During the early part of the American Civil War, Zeilin was on garrison duty in command of Marine Barracks, firstly at Philadelphia and later at Washington, D.C. Five days later, he was appointed to the regular rank of major.

On July 21, 1861, he commanded a company of U.S. Marines during the First Battle of Bull Run and received a slight wound.

[10] This article incorporates public domain material from websites or documents of the United States Marine Corps.