Here are 10 facts about the holiday, which falls on May 29 this year:
• Even though numerous communities had been independently celebrating Memorial Day for years, the federal government declared Waterloo, N.Y. the official birthplace of Memorial Day. Waterloo first celebrated the holiday on May 5, 1866.
• Memorial Day was celebrated on May 30 for decades, but in 1971, Congress established Memorial Day as the last Monday in May and a federal holiday.
• Memorial Day originally honored military personnel who died in the Civil War (1861-1865).
• Roughly 620,000 Americans died in the Civil War — making it the deadliest war in American history. About 644,000 Americans have died in all other conflicts combined.
• President Bill Clinton signed the National Moment of Remembrance Act on Dec. 28, 2000, designating 3 p.m. local time on Memorial Day as a National Moment of Remembrance.
• It wasn't always Memorial Day — it used to be known as Decoration Day.
• Red poppies are known as a symbol of remembrance, and it's a tradition to wear them to honor those who died in war.
• Even though Memorial Day began as a holiday honoring Union soldiers, some states still have Confederate observances. Mississippi celebrates Confederate Memorial Day on the last Monday of April, Alabama on the fourth Monday of April, and Georgia on April 26. North and South Carolina observe it on May 10, Louisiana on June 3 and Tennessee calls that date Confederate Decoration Day. Texas celebrates Confederate Heroes Day on Jan. 19 and Virginia calls the last Monday in May Confederate Memorial Day.
• The crowd that attended the first Memorial Day ceremony at Arlington National Cemetery was about the same size as those that attend today's observance: about 5,000 people
Ashley May contributed to this report.