Neill, Thomas Hewson was born on April 9, 1826 in Philadelphia, Pennsylvania, United States. Son of Doctor Henry and Martha (Duffield) Neill.
Graduated from the United States Military Academy, 1847.
Commissioned Second lieutenant 5th Infantry, United States Army, 1847. Assistant professor of drawing United States Military Academy, 1853-1857. Served as captain in Utah expedition and in New Mexico, 1857-1861.
Commissioned colonel 23d Pennsylvania Volunteers, 1862, served at siege of Yorktown. Brevetted major, 1862, promoted brigadier general United States Volunteers, 1862, brevetted lieutenant colonel, then colonel, 1863. Brevetted brigadier general United States Army, 1865, major general United States Volunteers.
Inspector general United States Army, 1867-1869 with headquarters at New Orleans. Commissioned lieutenant colonel, 1869. Commandant of cadets United States Military Academy, 1875-1879.
Known as Beau Neill.
Married Eva Looney, November 20, 1873, 3 children.