Civil War Union Brigadier General. Born in New York City, New York, he later would move with his family to Meadville, Pennsylvania. He graduated from West Point 3rd in the 43-man class of 1833. His high academic ranking gained him a position in the construction engineers, where he helped build harbor fortifications in his native city as well as in Boston, Newport, New London, Annapolis, and Charleston. When the corps was expanded in 1838, he was promoted to Captain, a rank he held for the next 23 years. During that period he also taught engineering at his alma mater and for 2 years was on inactive duty due to poor health. Early in the Civil War, he served as aide-de-camp to Winfield Scott, commanding general of the army, then took a position with the United States Sanitary Commission. Promoted to Brigadier General of Volunteers on November 1, 1861, he became chief of staff and chief engineer to Major General Henry W. Halleck, then commanding the Department of the Missouri and later the Department of the Mississippi. After serving in the advance on Corinth, he accompanied Halleck to Washington when the latter replaced Major General George B. McClellan in army command. Retaining the rank of engineer, he was promoted to Lieutenant Colonel of Regulars on March 3, 1863. In September 1864 he left Halleck's staff and spent the next 2 years as the Superintendent of the United States Military Academy. Later he held posts on engineering boards and engaged in other assignments with his corps until he retired, with the rank of Colonel and brevet Major General, on January 13, 1874. In civilian life he resided in New York City, married the widow of his former boss and close friend General Halleck, (she was the granddaughter of American patriot Alexander Hamilton), and pursued scientific and philanthropic endeavors. From 1877 until his death he was vice president of the American Geographical Society of New York, and wrote and translated monographs on engineering. In retirement he also wrote histories of the Revolution and the War of 1812, and updated a work originally published in 1850: Biographical Register of the Officers and Graduates of the United States Military Academy. This was a most important work, for it gave birth to the "Culllum Number." This number is the system of numbering graduates and keeping their biographical data. The Academy has always held the stance that no graduate has ever held a deeper affection for the Academy or a greater pride in the achievements of its graduates than he. A 3rd edition of this major reference work was released a year before his death from pneumonia in New York City. In accordance with his will, supplements were added to the set in 1900, 1910, and 1920. Since he had no descendants, again in accordance with his will, he bequeathed his fortune to his living relatives and those of General Halleck, and to museums, hospitals, libraries, churches, and the American Geographical Society, with the largest part of his bequest going to the United States Military Academy.