Peter Augustus Porter was a lawyer, politician, and member of the Breckinridge family and a Union Army colonel in the American Civil War. He died in the Battle of Cold Harbor.

The Battle of Cold Harbor was fought during the American Civil War near Mechanicsville, Virginia, from May 31 to June 12, 1864, with the most significant fighting occurring on June 3. It was one of the final battles of Union Lt. Gen. Ulysses S. Grant's Overland Campaign, and is remembered as one of American history's most unnecessary and lopsided battles. Thousands of Union soldiers were killed or wounded in a hopeless frontal assault against the fortified positions of Confederate Gen. Robert E. Lee's army.