Not being a native of Massachusetts, I had never even heard of Patriot's Day until I moved here in the mid '90s.  

And then, I was thinking it had something to do with the New England Patriots football team.  But that thought did not last long, so I looked it up.  Patriot's Day is a civic holiday in Massachusetts and Maine (once part of Massachusetts) commemorating the anniversary of the Battles of Lexington and Concord, the first battles of the American Revolutionary War.   Since 1969, the holiday has been observed on the 3rd Monday of April, providing a three-day long weekend, as well as the first day of public school vacation here as well as in Maine.

Prior to that, it had been designated as April 19.  The Boston Marathon is run on Patriots' Day every year, so some people know the holiday as "Marathon Monday."  The Red Sox have traditionally been scheduled to play at Fenway Park on the holiday ever since 1959.  The games begin early and the marathon runners usually reach Kenmore Square near the middle of the game.

So whether you watch the marathon, the Red Sox, or simply relax, keep in mind the real reason for this Monday holiday here in Massachusetts.