Why is the date, April 14, 1775 a milestone in American History?

Concord is a village twenty miles northwest of Boston, and was the objective of a British expedition in 1775 that opened the War of Independence with the Battle of Lexington and Concord. On April 14, 1775, General Thomas Gage received secret orders from the Earl of Dartmouth to proceed against the "open rebellion" that existed in the colony, even at the risk of conflict. Gage decided to move quickly against the major militia's supply depot at Concord.  On the night of April 18, Lt.Col Francis Smith and Maj. John Pitcairn of the marines gathered 700 men and set out for Lexington and Concord to destroy the supplies over there. But local patriots got wind of the plan and sent Paul Revere and William Dawes by separate routes on their famous ride to spread the alarm in Lexington and Concord.