Millions of workers and school children in the United States have the day off Monday for the annual Presidents' Day holiday.
It is officially known as Washington's Birthday, which became a federal holiday in 1879 to celebrate the February 22 birthday of the first U.S. president, George Washington.
But over time the celebration evolved to include the February 12 birthday of the 16th president, Abraham Lincoln, as well. Lincoln was never honored with an official federal holiday, although many states celebrated a day in his honor.
In 1968, Congress passed a law shifting the celebration of several federal holidays to predetermined Mondays in order to give people three-day weekends instead of a single day whenever that date happened to hit during the week.
Washington's Birthday became the third Monday each February, and by a quirk in the calendar, the holiday can never fall on Washington's actual birthday.
The first president was also the first individual American to get a federal holiday celebrating his life. Martin Luther King Jr., who has been honored with a January holiday since 1986, was the second.