"Memorial Day is a United States federal holiday observed on the last Monday of May (May 25 in 2009). Formerly known as Decoration Day, it commemorates U.S. men and women who died while in the military service. First enacted to honor Union soldiers of the American Civil War (it is celebrated near the day of reunification after the civil war), it was expanded after World War I to include American casualties of any war or military action."
Flying the American Flag at Half-Staff
An easy way to remember when to fly the United States flag at half-staff is to consider when the whole nation is in mourning. These periods of mourning are proclaimed either by the president of the United States, for national remembrance, or the governor of a state or territory, for local remembrance, in the event of a death of a member or former member of the federal, state or territorial government or judiciary. The heads of departments and agencies of the federal government may also order that the flag be flown at half-staff on buildings, grounds and naval vessels under their jurisdiction.
On Memorial Day the flag should be flown at half-staff from sunrise until noon only, then raised briskly to the top of the staff until sunset, in honor of the nation’s battle heroes.
source: United States Department of Veteran's Affairs
Take a moment to thank all our veterans and to remember those who've died in service to our great country today.