The events of the battle are commemorated on the third Monday of every April in a statewide Massachusetts [1] holiday called Patriot’s Day, when costumed interpreters reenact the events of that long-ago April morning. You’ll have to get up pretty early to see them—the first shots on Lexington Green are fired, in keeping with history, at 6 in the morning, with events transpiring along the Battle Road for the rest of the day.
Links:
[1] http://www.moon.com/destinations/new-england/massachusetts