We Are One: This map, probably drawn by British Lieutenant Richard Williams, depicts the positions of the British and American troops in October 1775. The map delineates the envelopment of the city by "rebel" forces that led to the British evacuation of Boston on March 17, 1776. Williams's map features the Continental Army Headquarters in Cambridge and the fortifications constructed by American troops. His manuscript map was sent to London where it was engraved and printed less than two weeks before the British troops left the city. British military and political leaders used maps like this to gain a better sense of the American war.