Here's a look at what you need to know about Arlington National Cemetery in Virginia.
Facts: Arlington National Cemetery in Arlington, Virginia contains the remains of more than 300,000 people from the Unites States and eleven other countries, buried there since the 1860's.
More than 4 million people visit the cemetery annually.
It averages about 5,000 funerals each year.
The Arlington Estate was originally owned by George Washington Parke Custis, adopted grandson of George Washington. His daughter Mary Ann Randolph, who married Robert E. Lee, inherited the estate. It was abandoned by the Lees during the Civil War and used as headquarters for the Union army.
Arlington house (also known as Custis-Lee Mansion) is currently a memorial for Robert E. Lee and run by the National Park Service.
The cemetery has the second-largest number of people buried of any national cemetery in the U.S. Calverton National Cemetery, on Long Island, near Farmingdale, New York has the most people buried and conducts more than 7,000 burials each year.
Arlington averages 28 funerals, including interments and inurnments, a day.
The flags in Arlington National Cemetery are flown at half-staff from a half hour before the first funeral until a half hour after the last funeral each day.
Funerals are normally conducted five days a week, excluding weekends.
Arlington National Cemetery is administered by the Department of the Army.
Based on its burial rate, the cemetery is expected to reach capacity by 2020, after which time it will operate as a national shrine.
The partial remains of the seven astronauts who died aboard the Space Shuttle Challenger on January 28, 1986 are buried at Arlington National Cemetery.
The seven Columbia astronauts have their own memorial at Arlington, near the one for the Challenger.
As a living tribute, there are 36 Memorial Trees for the Medal of Honor recipients.
Burial in Arlington is generally limited to active, retired, and former members of the armed forces, Medal of Honor recipients, high-ranking federal government officials and their dependents.
Annually just prior to Memorial Day weekend the 3rd U.S. Infantry (The Old Guard) place American flags before all the gravestones and niches of service members buried at Arlington National Cemetery and the U.S. Soldier's and Airmen's Home National Cemetery.
Nearly 5,000 unknown soldiers are buried at Arlington National Cemetery.
The Tomb of the Unknowns (aka Tomb of the Unknown Soldier) has never been officially named. It is a memorial to the dead of World Wars I and II, the Korean War and the Vietnam War.
The Tomb is made from Yule marble quarried in Colorado. It consists of seven pieces, with a total weight of 79 tons. The Tomb was completed in 1932, at a cost of $48,000.
The tomb has the following words inscribed: Here rests in honored glory An American Soldier Known but to God.
The Tomb is guarded 24 hours a day, 365 days per year by volunteer members of 3rd U.S. Infantry Regiment (The Old Guard), in full dress uniform carrying M-14 rifles.
Timeline: June 15, 1864 - Quartermaster General Montgomery Meigs designates Arlington House and its surrounding 200 acres as a Union military cemetery.
1882 - George Washington Custis Lee sues the government for taking over the land. The U.S. Supreme Court rules that the federal government was trespassing.
March 3, 1883 - Congress purchases the land for $150,000.00.