Residents across Massachusetts and Maine will celebrate Patriots’ Day Monday to commemorate the opening battles of the American Revolution at Lexington and Concord in 1775. The special holiday is observed only in those two New England states, as Maine was part of the Bay State until the early 19th century.

Here’s everything you need to know about Patriots’ Day, including interesting facts, related events and what’s open and closed in both states for the 241st anniversary.

What were the Battles of Lexington and Concord?

The Battles of Lexington and Concord on April 19, 1775, marked the first military engagements of the American Revolutionary War — an open armed conflict between Great Britain and 13 of its North American colonies which had declared themselves as the independent United States of America. They took place in the Province of Massachusetts Bay, one of the 13 original U.S. states, within the neighboring towns of Lexington, Concord, Lincoln, Cambridge and present-day Arlington.

Hundreds of British soldiers marched from Boston to nearby Concord on the night of April 18 to destroy an arms cache collected by the American colonists. Paul Revere and other riders alerted colonial Minutemen of the plan, who then mobilized to intercept the Redcoats.

The British army outnumbered the Americans on the battlefield in Lexington and headed for Concord shortly after. But they were surprised by a counterattack from the colonists upon their arrival, forcing the Redcoats to hastily retreat to Boston. That day, 49 Americans and 73 British were killed. The fighting proved to the American colonists that they could defeat the British. After years of warfare when the cause often seemed lost, the colonies formally won their independence from Great Britain in 1783.

What’s open and what’s closed?

Banks, post offices, federal courts, financial markets and most retailers, including liquor stores and supermarkets, will be open Monday in Massachusetts and Maine. State courts and the registry of motor vehicles, however, will be closed. Public schools are also not in session, as part of a weeklong spring break.

How can I celebrate?

If you’re in the Concord or Lexington area for Patriots’ Day this year, check out these fun events via the National Park Service to mark the state holiday:

Capt. David Brown’s company of Minutemen re-enactors is scheduled to demonstrate drill maneuvers and musket firings at the North Bridge, which spans the Concord River, Saturday from 7 a.m. to 11:30 a.m. local time and at the Concord Museum on Cambridge Turnpike from 1 p.m. to 5 p.m.

Visit the Whittemore House on Marett Street in Lexington Saturday between 10 a.m. and 1 p.m. and discover what life was like on April 19, 1775.

Gather at the Battle Road Trail at the Minute Man National Historical Park on Liberty Street in Concord on Saturday at 2 p.m. to watch hundreds of British and colonial re-enactors dramatically restage the running skirmish that took place on this long stretch of road on the border of Lincoln and Lexington.

Visit the historic house of Col. James Barrett on Barrett’s Mill Road in Concord on Sunday from 1 p.m. to 4 p.m. to learn about the military preparations that helped launch the colonies into the Revolutionary War.

Watch British and colonial re-enactors commemorate the “shot heard around the world” with a restaging of the North Bridge fight featuring marching and musket fire at the North Bridge on Monday at 8:45 a.m. The Concord Parade will arrive at the bridge around 9:30 a.m. with ceremonies featuring Minuteman companies, Redcoat re-enactors and musical performances.