Gen. Benham was born in Connecticut. He graduated from West Point in 1837, first in his class. He was immediately promoted to the rank of Brevet Second Lieutenant in the Corps of Engineers. Washington. He served in the civil war from 1861 to 1866, first as Engineer of the Department of the Ohio. He was brevetted Colonel for gallant conduct at the battle of Garrick's Ford, Virginia in 1861. For most of the war he served as an engineer and superintended the construction of numerous fortifications and ponton bridges.

After the war he continued to serve in the Corps of Engineers until his retirement in 1882 after 45 years service.