Henry Brewerton was born in New York City, New York. He lost his parents at a very early age, but, under the guardianship of future governor of New York and vice president of the United States
Daniel D. Tompkins, entered the
United States Military Academy at
West Point, New York, two months before his 12th birthday – making him the youngest cadet in the history of West Point. He graduated on July 1, 1819, 5th in a class of 29 cadets and was commissioned a second lieutenant the same day. After a brief tour at
Rouses Point helping to survey and establish the 45th parallel along the border between the United States and
Canada, Brewerton taught engineering at the academy. Apparently, his survey of Rouse's Point was inaccurate as it was later discovered that
Fort Montgomery had been built on land that really belonged to Canada. This resulted in the boundary line being shifted. After a year at West Point, Brewerton had a number of temporary assignments building fortifications in Delaware, Georgia and New York Harbor. He oversaw construction of
Fort Jackson in Louisiana from 1824 to 1827 and at
Fort Adams in
Newport, Rhode Island, from 1827 to 1828. During his stay in Newport, his wife died. He was promoted to first lieutenant on January 1, 1825. Brewerton then served as superintending engineer of the construction of the defenses of
Charleston Harbor from 1828 to 1832 and then of the
Cumberland Road (a.k.a. National Road), one of the country's first highways, in Ohio from 1832 to 1836. He was promoted to captain on September 21, 1836. ==Civil War service==