Soldier, rest! Thy warfare o'er,
Sleep the sleep that knows not breaking,
Dream of battled fields no more.
Days of danger, nights of waking.
-Sir Walter Scott
After the Civil War, the government created a holiday to honor the Union and Confederate soldiers who had died in battle. Union general John Logan chose May 30th because it did not honor the anniversary of any battle.
When World War I ended, they extended the idea to honor all United States soldiers who died in any war.
In 1968, Congress's Uniform Holidays Act severed the link between Memorial Day and the original date, changing it instead to "the last Monday in May" to allow for a three-day weekend.
Memorial Day has become a holiday for families to remember anyone they have lost (veteran or otherwise), to lay flowers at grave sites.
For those unable to travel to the graves of their loved ones, there are websites like FindAGrave.com, where one can create a cyber-monument and leave a "virtual" note or bouquet.