Today is Memorial Day, a national observance once known as Decoration Day. This day was initially established to honor the Civil War dead by decorating their graves. Over time, the holiday expanded to include all those who gave “the last full measure of devotion” for the nation.

Across the country today, American flags will be flown at half-mast until noon. In a beautiful tradition known as “Flags In,” soldiers of the 3rd U.S. Infantry Regiment — “The Old Guard” — have placed flags at hundreds of thousands of gravestones at Arlington National Cemetery. As they have done every year since 1948, Third Infantry soldiers will remain at the military cemetery throughout the holiday weekend to make sure the flags stay in place.