Heintzelman was born in Manheim, Pennsylvania, to Peter and Ann Elizabeth Grubb Heintzelman. He graduated from the United States Military Academy in 1826 and was commissioned a brevetsecond lieutenant in the 3rd U.S. Infantry, July 1, 1826, then in the 2nd U.S. Infantry and served on the Northern frontier at Fort Gratiot, Fort Mackinac, and Fort Brady. On March 4, 1833, he was promoted to first lieutenant and served on quartermaster's duty in Florida during the Second Seminole War. On July 7, 1838, he was appointed captain in the Quartermaster's Department, remaining in Florida with the 2nd Infantry until the close of the war in 1842. In 1847, during the Mexican–American War, he joined General Winfield Scott's army in Mexico, taking part in several engagements, for which he was appointed brevet major on October 9, 1847. In 1848–49 he accompanied his regiment around Cape Horn to California, and for several years served in California and the Arizona Territory. In December 1851, Major Heintzelman led the Yuma Expedition from the post of San Diego to put down the Yuma uprising, called the Yuma War. His expedition established Fort Yuma and peace was made in October, 1852. He received the brevet of lieutenant colonel for his conduct in the campaign against the Yuma Indians and on March 3, 1855, he was promoted to major of the 1st U.S. Infantry and served with that regiment on the Texas frontier. In 1859, during the First Cortina War in Texas, he was largely responsible for the defeat of Juan Cortina's forces. Heintzelman was the first president of the Sonora Exploring and Mining Company which established the Cerro Colorado, Arizona, mining town in southern Arizona. The town became famous during the American Civil War for the massacre of mine employees by Mexican outlaws and for buried treasure.
Civil War
When the Civil War began, Heintzelman was promoted to colonel of the 17th U.S. Infantry and brigadier general of volunteers in May 1861. He led a division at First Bull Run in July and was wounded in the elbow. Heintzelman was in overall command of the 2nd Michigan Infantry regiment that was responsible for the raid, ransacking, and devastation of Pohick Church in Lorton, Virginia, on November 12, 1861. The historic church was built in 1769 by George Washington, George Mason, and George William Fairfax, among others, and restored after the War of 1812 by President Martin Van Buren, John Quincy Adams, and Francis Scott Key, among others. This ransacking caused the loss of a myriad of irreplaceable artifacts. In March 1862, President Lincoln organized the Army of the Potomac into corps, and Heintzelman received the III Corps of the Army of the Potomac in the Peninsula Campaign. His corps played a prominent role in the siege of Yorktown where Heintzelman and division commander Fitz John Porter were among the first to use the Union Army Balloon Corps. The corps bore the brunt of the fighting at Williamsburg and saw significant action at Fair Oaks, Oak Grove, and Glendale. His corps was temporarily attached to the Army of Virginia and took part in the Second Battle of Bull Run. He was commissioned as a brevet brigadier general in the regular army for the battle of Fair Oaks and a major general of volunteers for the battle of Williamsburg. At the Battle of Glendale, Heintzelman was bruised in the wrist by a spent bullet and was unable to use his left arm for a few weeks. After the Seven Days Battles, he was promoted to major general of volunteers to rank from May 5. His popularity and confidence in the army were eclipsed by the aggressive nature of his subordinate division commanders Joseph Hooker and Philip Kearny, and he did not display any notable leadership or tactical prowess in either the Peninsula Campaign or Second Bull Run, although following the Union retreat from Gaines Mill, he was one of three corps commanders to advocate launching a counterattack against the Army of Northern Virginia. The Second Bull Run campaign had been very hard on the III Corps, which sustained heavy losses, including one of its division commanders, and had come close to being driven from the field in panic. On September 4, Heintzelman was relieved from command, being judged as too old and insufficiently aggressive. He spent the remainder of the war commanding the Washington defenses. At war's end in 1865, Heintzelman reverted to the rank of colonel in the regular army. He served on army boards of inquiry and on occupation duty in Texas as part of Reconstruction. Heintzelman retired on February 22, 1869 and was granted a promotion to major general, entitling him to the pension of that rank. He died in Washington, D.C., on May 1, 1880, at the age of 74. He is buried in Forest Lawn Cemetery, Buffalo, New York. According to his doctor, he died of complications arising from an attack of pleurisy during the Peninsula Campaign eighteen years earlier. His grandson Stuart Heintzelman, a West Point alumnus of the class of 1899, served in World War I and rose to the rank of Major General.
