Memorial Day is Monday, but there's more to the nationwide observance than just taking a three-day weekend and a day off from work. The holiday recognizes people who died serving in the United States military. The tradition has developed a rich history over the past 150 years.

Memorial Day started out as Decoration Day, which unofficially began around the time the Civil War ended, when people began visiting the graves of fallen soldiers. Various cities claim to have originated the tradition, but Waterloo, New York, won out in 1966 when President Lyndon B. Johnson officially designated it the birthplace of Memorial Day.

As such, the first official Decoration Day took place in Waterloo on May 5, 1868. The Grand Army of the Republic, a group of former Union soldiers, requested the observance. The organization's leader, Gen. John A. Logan, said the day should be designated "for the purpose of strewing with flowers or otherwise decorating the graves of comrades who died in defense of their country during the late rebellion, and whose bodies now lie in almost every city, village and hamlet churchyard in the land," according to the History Channel.

Here are more facts about Memorial Day, collected from Mental Floss, the U.S. Department of Veterans Affairs and dealnews: