Winthrop was born in
New Haven, Connecticut, and is a descendant of several prominent Colonial families. Through his father, he was descended from Governor
John Winthrop, and through his mother, from theologian
Jonathan Edwards, as well as early settlers George (Joris) Woolsey and Thomas Cornell. He graduated in 1848 from
Yale University, where his uncle
Theodore Dwight Woolsey was President, and he was a member of the Phi chapter of the
Delta Kappa Epsilon fraternity. He traveled for a year in Great Britain and Europe and then through the United States, settling in
Staten Island in the 1850s. After contributing to periodicals, short sketches, and stories, which attracted little attention, Winthrop enlisted in the
7th Regiment, New York State Militia, an early volunteer unit of the
Federal Army that answered
President Abraham Lincoln's call for troops in 1861. He wrote a popular essay about the experience titled "Our March to Washington." He was appointed Major and soon became an
aide-de-camp to
Major General Benjamin Butler, commander of the Department of Virginia headquartered at
Fort Monroe. Winthrop had long been an abolitionist, along with his younger brother
William Winthrop, who later became the nation's leading authority on military law. Butler credited Winthrop with first formulating the policy that automatically conferred freedmen status on escaped slaves who entered into Union Army-held territory. ==Battle of Big Bethel==