The World War II Liberty ship SS Samuel Heintzelman, launched on 30 September 1942, was named in his honor.

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.

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 unit on the Texas frontier.

The town became famous during the American Civil War for the massacre of mine employees by Mexican outlaws and for buried treasure.

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.

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.

[4] The Second Bull Run campaign had been 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.

[5] 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.