A descendant of both John Winthrop, first Governor of Massachusetts, and John Winthrop, the Younger, first Governor of Connecticut, immediately after graduating he became a personal secretary to future president William Howard Taft while Taft was Governor-General of the Philippines. Winthrop was soon promoted to Assistant Executive Secretary of the Philippines (1901–1903) and was appointed as a Judge of the Court of First Instance, Philippine Islands (1903–1904).
A direct descendant of both John Winthrop, Massachusetts' first governor, and John Winthrop, Connecticut's first governor, immediately after graduation he became William Howard Taft's personal assistant while Taft was governing the Philippines. Winthrop was soon promoted to a key role in the Philippines (1901–1903) and later appointed as a judge in the Philippine Islands' court system (1903–1904).