Civil War Union Brigadier General. He was born in Kent County, Delaware, and was a graduate of the West Point class of 1836, ranking 22nd among 49 cadets. He was assigned to the 2nd United States Artillery and was sent to Florida to oppose the Seminole uprising. On September 12, 1837, he resigned his commission and spent four years on his Delaware farm until he was appointed professor of mathematics in the United States Navy. He taught aboard ships, then at a naval facility in Philadelphia, and finally at the newly opened Naval Academy, in Annapolis, Maryland. During the Mexican War he served aboard the USS United States off the coast of California coast. In 1851 he transferred to the chair of field artillery and infantry tactics, with the additional duty of professor of astronomy. With the outbreak of the Civil War, he returned to army service as Colonel of the 1st Delaware Infantry. On August 8, 1861, he was appointed Brigadier General of Volunteers. Soon afterward he led an expedition to the eastern shore of Virginia, then took command of the prison at Point Lookout and the defenses of the lower Potomac. He did not see field service until Gettysburg, where he led a XII Corps brigade, composed primarily of Maryland regiments, in the Army of the Potomac. At the close of the campaign in Pennsylvania, his command was detached for garrison duty outside Harpers Ferry. He spent 5 months at this post before going to Baltimore, in December 1863, to succeed Major General Robert C. Schenck in charge of the Middle Department. Rejoining the Army of the Potomac the following spring, he directed a V Corps division at Cold Harbor. Afterward he was again detached to head a portion of the Middle Department, encompassing Baltimore and the eastern shore of Maryland. In July he led a conglomeration of provisional units against Lieutenant General Jubal A. Early's Confederate raiders; after the latter's retreat to Virginia, he returned to departmental duties. On his muster out, in August 1865, he returned to Annapolis, where he taught gunnery and other subjects of a mathematical, scientific, and tactical nature. In 1870 he was assigned to the Naval Observatory in Washington D.C., serving there until his retirement 6 years later. His remaining years were spent in Washington, where he later would die. Although a West Point man, because of his long service at the Naval Academy, he was accorded the distinction of burial in its cemetery at Annapolis. His tombstone remembers his service there, citing him as one of the founders. He was the father of Artic Explorer James Booth Lockwood, who lost his life during the "Lady Franklin Bay Expedition" while serving as second in command under Adolphus W. Greely.