Allen G. Brady was born on February 13, 1822, in Middlesex County, Massachusetts.

He became lieutenant colonel of the 3rd Connecticut Infantry Regiment, a 3 months regiment.

On August 28, 1862 he became captain of Company B of the 17th Connecticut Infantry. He had advanced to major by July 1, 1863, when at the Battle of Gettysburg he took command of the regiment when Lt. Colonel Douglas Fowler was killed.

Brady mustered out with his regiment on October 21, 1863, but returned to service as major in the Veteran Reserve Corps. On July 28, 1866 he became Lieutenant of the 43rd Infantry, and mustered out on March 4, 1867.

He died on February 11, 1905 in Fayetville, North Carolina.