Todd served in the Virginia legislature in 1776 and then participated in the expedition led by George Rogers Clark against Kaskaskia and Vincennes that captured the Illinois Country from the British in 1778. With Clark as commandant of the entire territory north and west of the Ohio river, Todd was appointed as County Lieutenant and Civil Commandant of "Illinois County", which had been organized by the Virginia legislature in 1778 with the government based in Kaskaskia.