He founded Fort Abercrombie in what is now North Dakota in 1857, selecting the site and supervising construction of the wooden fort. He then commanded the garrison until promoted and reassigned to duty in Minnesota.
Civil War service
By the start of the Civil War, at the age of 63, Abercrombie was one of the oldest field officers in both the Union and Confederacy. He served as the commanding officer of the 7th U.S. Infantry in Minnesota with the full rank of colonel in the Regular Army.
After the conclusion of the Peninsula Campaign, Abercrombie was replaced as commander in favor of younger officers and spent the next year involved in the defense of Washington, D.C., and, in 1864, headed various Union supply depots in Virginia during the Overland Campaign. Abercrombie commanded the troops that defended a depot in Fredericksburg, Virginia, in June 1864 against an attack by Hampton's Legion.
On March 13, 1865, Abercrombie was brevetted a brigadier general in the Regular Army in recognition of his long service.[3] Abercrombie retired from active duty on June 12[4] after commanding Fort Schuyler in New York.
Postbellum
In his retirement, Abercrombie stayed associated with the U.S. Army. He served on court-martial duty for the next 3 years.
Linedecker, Clifford L., ed. Civil War, A-Z: The Complete Handbook of America's Bloodiest Conflict. New York: Ballantine Books, 2002. ISBN0-89141-878-4