Andrew Humphreys was born into a prominent Philadelphia family of Quaker origin. His grandfather, Joshua Humphreys, a distinguished naval architect later known as the “Father of the American Navy,” served as chief naval constructor (1794–1801) and designed the first U.S. warships, including the Constitution (“Old Ironsides”) and her five sister ships. Andrew’s father, Samuel, also served as chief naval constructor (1826–46) and designed and built the U.S.S. Pennsylvania, the largest ship in the world at the time and the most heavily armed man-of-war ever built. Despite his pedigree, young Andrew forsook a promising career in the navy for the hardscrabble life of a soldier. He graduated from West Point in 1831 and joined the 2nd Artillery Regiment at Ft. Moultrie, South Carolina, though, as a gifted draftsman and engineer, he did occasional topographical duty as well. At the outset of the 2nd Seminole War (1835–42), Humphreys accompanied his regiment to Florida where he saw combat in the spring and summer of 1836. Severe illness, probably yellow fever, forced him from the army in September, and he worked intermittently as a civil engineer before returning to uniform in 1838.
Early in his second hitch, Humphreys served with the newly organized Army Corps of Topographical Engineers on assignments in Chicago, New York, and Washington, D.C., conducting surveys and overseeing harbor improvements and bridge building. In 1844 at the behest of internationally renowned scientist Alexander Dallas Bache, Humphreys detailed as “assistant in charge” at the Coast Survey while Bache transformed that organization into the preeminent patron of antebellum science in the United States. Humphreys left his position in 1850 to assume responsibility for an extensive survey of the lower Mississippi River, an assignment that he embraced with characteristic vigor. The compilation of that work, the massive Report upon the Physics and Hydraulics of the Mississippi River (1861), co-authored with his talented young assistant, Henry L. Abbot, represented the most thorough analyses of the Mississippi River ever completed, won the respect of engineers around the world, and decidedly influenced the development of river engineering in America. During that same period and under the immediate supervision and close cooperation of the Secretary of War Jefferson Davis, Humphreys also directed the Pacific Railway Surveys (1853–57), an unprecedented assemblage of more than one hundred soldiers, scientists, and technicians marshaled for the single purpose of identifying the most practical and economical route for the nation’s first transcontinental railroad. The enormous thirteen-volume final report on the various expeditions was a monumental scientific achievement and a virtual encyclopedia of the western experience. By the eve of the Civil War, Humphreys ranked among the upper echelon of American scientists and had earned membership in the prestigious American Philosophical Society.
While the war accelerated the traditionally slow pace of promotion in the army, Humphreys—who had not seen combat in twenty-five years—found few early opportunities for advancement. Neither a Republican nor an ardent emancipationist, he also suffered for his very public association with Confederate president Jefferson Davis and, later, for his friendship with former Army of the Potomac commander, Maj. Gen. George B. McClellan. More than two hundred Union officers outranked him as late as August 1862, but Humphreys eventually proved his mettle in the field. He won brevet promotions for bravery at Fredericksburg, where he led a green division in a gallant charge on Marye’s Heights, and again at Gettysburg, where he and his division fought doggedly in retreat, resisting a slashing Confederate attack along Emmetsburg Road in some of the fiercest fighting of the war. For his efforts, he earned the moniker, “the Fighting Fool of Gettysburg.” Humphreys afterwards became chief of staff of the Army of the Potomac under Maj. Gen. George Gordon Meade during the tragic encounters at the Wilderness and Cold Harbor as well as the early siege of Petersburg. In November 1864, he took command of the celebrated II Corps and earned additional accolades at Sailor’s Creek, contributing in no small part to Robert E. Lee’s final surrender at Appomattox Courthouse. At war’s end, Charles Dana, Assistant Secretary of War, called Humphreys “the great soldier of the Army of the Potomac.”
General Ulysses S. Grant selected Humphreys as the new chief of the Corps of Engineers in 1866, a position he held for thirteen years. During his long tenure, he confronted a dramatic postwar expansion of internal improvements and oversaw important surveys and explorations of the American West as well as a complete overhaul of the nation’s coastal fortifications. He also established the army’s first engineer school at Willets Point in New York and served on a number of important boards and commissions, including the Washington Monument Commission, the Lighthouse Board, and the Commission to examine into Canal Routes across the Isthmus connecting North and South America. He retired at the age of 68 and is the second-longest serving chief, second only to Brig. Gen. Joseph G. Totten. Humphreys’ last years were devoted to penning two important and highly reputable histories of the Virginia campaigns. He died in Washington, D.C., on December 27, 1883.