Beauregard was born a member of a prominent Louisiana family, and graduated in 1838 from West Point and fought in the Mexican War. In April 1861, Beauregard commanded Confederate troops at Charleston, where he initiated the bombardment of Fort Sumter, the first official conflict of the war. He also played a major role in the first Battle of Bull Run on July 21, 1861.

In April 1862, Beauregard took command on the western front, but illness soon forced him to retire. He later defended the south Atlantic coast. In 1864 he fought in Virginia and then commanded troops in Alabama, Mississippi, and Tennessee. After 1865, Beauregard was active in the railroad industry, managed the Louisiana state lottery, and defended his military reputation.