Heintzelman, Samuel Peter was born on September 30, 1805 in Manheim, Pennsylvania, United States. Son of Peter and Ann (Grubb) Heintzelman.
Graduated from the United States Military Academy, 1826.
Commissioned captain United States Army, 1838. Served in battles of Pasolos Ovejas, Huamantla and Atexco in Mexican War, 1846-1848. Brevetted major, 1847.
Promoted to major 1st Infantry in California, 1855. Founder Fort Yuma (Arizona). Commissioned colonel 17th Infantry, 1861, brigadier general United States Volunteers, 1861.
Commanded 3rd Division, United States Army under General Irvin McDowell at 1st Battle of Bull Run. Commanded III Corps. right wing of army under General John Pope, 2d Battle of Bull Run, 1862. Took part in Peninsula campaign, battles of Malvern Hill and Seven Days.
Promoted major general United States Volunteers, 1862, participated in battles of Williamsburg, Seven Pines and Fair Oaks. Assigned to defenses of Washington, District of Columbia, 1862-1863. Sent to command Northern (Central) States Department, 1864.
Command 17th Infantry in Texas, 1865-1869. Promoted general, retired 1869.