Patriots' Day is a public holiday celebrated in the United States, primarily in Massachusetts and Maine. It commemorates the battles of Lexington and Concord, which marked the beginning of the American Revolutionary War on April 19, 1775. The holiday is observed on the third Monday in April. On Patriots' Day, various events take place, including parades, reenactments, and community activities. One of the most notable events is the Boston Marathon, which occurs on the same day, attracting runners and spectators from around the world. The day serves as a reminder of the sacrifices made for American independence.