Highlighted on this fine topographic map of Boston and vicinity are the British and American troops. The American troops are colored red -- the first corps in Cambridge, the second corps opposite Charlestown neck, and the third corps near Roxbury. Among the many strategic topographic features so excellently rendered on this map is Dorchester Heights, which appears devoid of British defensive forces. This serious tactical error was ultimately recognized by General Washington, who occupied the Heights and forced the British to withdraw from the city on March 17, 1776. A note on the map reveals that it is based on an original plan of the siege drawn by order of the British government. Interestingly, the British fortifications on Boston Neck and Castle William Island are greatly exaggerated.