After the war he spoke in favor of civil and voting rights for the recently freed slaves, an opinion not common among high-ranking Confederates.
Beauregard's military writings include The Principles and Maxims of the Art of War, Report on the Defense of
Charleston, and A Commentary on the Campaign and
Battle of Manassas.
Beauregard and Jefferson Davis published a series of bitter accusations and counter-accusations, blaming each other in retrospect for the defeat of the Confederacy.
General Beauregard declined offers to take command of the armies of Romania (1866) and Egypt (1869).
He became involved in promotion of railroads, both as a company director and a consulting engineer. He invented a system of cable-powered street railway cars.
He served in the government of the State of Louisiana, first as adjutant general, and then less successfully as manager of the Louisiana State Lottery. Though considered personally honest, he failed to reform corruption in the Lottery system.
P.G.T. Beauregard died in
New Orleans. He was buried in Metairie Cemetery.