His parents were Creole, being descendants culturally related to the original French settlers of the Southern United States, especially Louisiana, resulting in Pierre speaking French before learning English. This proved an asset for him at West Point, where he read the classics on the art of war in French. In 1838 he graduated second in a class of forty-five. One of his friends and classmates was Irvin McDowell, who later fought for the Union, and whom Beauregard defeated at the Battle of First Bull Run. Following his graduation, Beauregard was commissioned a second lieutenant in the Corps of Engineers, and assigned to Fort Adams, outside Newport Rhode Island. In June of 1839 he was promoted to lieutenant and transferred to Pensacola, Florida, where he was placed in charge of constructing coastal defenses.
At the start of the Mexican War, he served again as an engineer under the command of General Winfield Scott. Wounded, he received two brevets for bravery. After this war, he continued overseeing the construction of fortifications on the coast. In January 1861, he was appointed the superintendent of West Point, however, because of his Southern sympathies and outspoken manner, only served a few days in this position. On February 20, 1861, Beauregard resigned his commission in the United States Army upon accepting the position of brigadier general in the Confederate army.
When the Civil War began in April 1861, General Beauregard was the commanding officer of the bombardment of Fort Sumter in Charleston harbor, South Carolina. Beauregard was able to control the shore line, as the United States army had retreated to Fort Sumter. On April 14, 1861, following two days of persistent bombarding by Beauregard, Fort Sumter, and its commanding officer U.S. Major Robert Anderson, surrendered, providing Beauregard and the South its first victory.
From this point, Beauregard would serve as second in command to General Joseph E. Johnston at the Battle of First Bull Run; and as well to General Albert Sidney Johnston at the Battle of Shiloh. In 1863-1864, he was in charge of directing the defenses at Charleston, and near war's end, he provided needed support to General Robert E. Lee near Richmond, Virginia.
As history discovered, Beauregard was a better engineer than a tactical military leader. He became very pompous, probably in part due to his tremendous popularity as a result of his victory at Fort Sumter. But, this attitude far exceeded his actual military abilities, although he was a good commander. His conceited demeanor, combined with his being quite critical of others, and his explosive French temperament, resulted in his not being looked upon favorably by his superiors. Consequently, near the end of the war, he was assigned as commander of the Military Division of the West, that proved to be basically an administrative position, that carried no military power. When Union General William T. Sherman was advancing to the sea, Beauregard was called upon to assist General Johnston in North and South Carolina in their attempt to stop Sherman. Unsuccessful, and following the surrender of Johnston and the end of the Civil War, General Beauregard returned to New Orleans.
P.G.T. Beauregard's postwar career included a presidency of a railroad, the supervisor of the Louisiana State Lottery, that damaged his reputation due to being corrupt, and a few years as Louisiana State adjutant general. Although he did receive offers from the Egyptian and Romanian governments to command armies, he refused all the requests.
Pierre G.T. Beauregard died in New Orleans on February 20, 1893.