https:// en.wikipedia.org/wiki/Battles_of_Lexington_and_Concord
From it, this:
The Battles of Lexington and Concord were the first military engagements of the American Revolutionary War.[9] The battles were fought on April 19, 1775 in Middlesex County, Province of Massachusetts Bay, within the towns of Lexington, Concord, Lincoln, Menotomy (present-day Arlington), and Cambridge. They marked the outbreak of armed conflict between the Kingdom of Great Britain and its thirteen colonies in America.
There you go.