Peter Sides was born in 1820 in Philadelphia, Pennsylvania. He was a merchant there before the war.

On September 4, 1861 he became Captain of Company A of the 57th Pennsylvania Volunteer Infantry Regiment. The regiment became part of the Third Corps, taking part in the Peninsula Campaign and the Second Bull Run Camaign. On September 15th Sides was promoted to lieutenant colonel, and on March 12, 1863, to colonel.

Sides commanded the 57th Pennsylvania at the Battle of Gettysburg, losing 115 casuaties out of the 207 men engaged in fighting north of the Peach Orchard on July 2. Sides was wounded in the left hand.

He returned to command the regiment until May 5, 1864 at the Battle of the Wilderness, when he was again wounded, tis time in the left arm. He did not return to command, and would be discharged for disability on November 28, 1864 due to his wound.

Sides returned to Philadelphia. He died on October 23, 1878, and is buried in Lawnview Cemetery in Rockledge.