The events in chronological order are as follows:
- The battles at Lexington and Concord (April 19, 1775)
- The British evacuation of Boston (March 17, 1776)
- The battle of Bunker Hill (June 17, 1775)
- The signing of the Declaration of Independence (July 4, 1776)
So, the first event that happened was the battles at Lexington and Concord.