(CNN)Here's a look at Arlington National Cemetery in Virginia.
Arlington National Cemetery in Arlington, Virginia contains the remains of more than 400,000 people from the Unites States and 11 other countries, buried there since the 1860s.
More than 4 million people visit the cemetery annually.
The Arlington Estate was originally owned by George Washington Parke Custis, adopted grandson of George Washington. His daughter Mary Anna Randolph Custis, 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.
Funerals are normally conducted six days a week, Monday through Saturday. Arlington averages 27 to 30 funerals, including interments and inurnments, each weekday. And six to eight services on Saturdays.
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.
Arlington National Cemetery is administered by the Department of the Army.
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 Unknown Soldier:
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 War I, World War 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.
May 13, 1864 - The first military burial takes place at Arlington Estate. Pvt. William H. Christman of the 67th Pennsylvania Infantry is buried.
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.
May 15, 1920 - Memorial Amphitheater is dedicated.
1921 - The Tomb of the Unknowns is established for the Unknown Soldier of World War I.
April 6, 1948 - The 3rd U.S. Infantry begins guarding the Tomb of the Unknowns 24 hours a day, 365 days a year.
May 14, 1998 - Through DNA testing, the Vietnam era Unknown Soldier's identity is established as Air Force 1st Lt. Michael Joseph Blassie who died near An Loc, Vietnam in 1972. His remains were returned to his family and this particular crypt remains empty.
November 13, 2009 - Secretary of the Army John McHugh orders the inspector general to conduct an inspection of the record keeping operations in Arlington National Cemetery.
June 2010 - The Army's investigation reveals missing burial records, unmarked graves and burial urns put in a spillage pile, where dirt dug up for gravesites is left. Longtime Superintendent John C. Metzler is reprimanded. He is able to keep his job until his retirement date of July 2, 2010.
July 14, 2010 - The cemetery announces that Thurman Higginbotham, second-in-command at Arlington, filed paperwork in the previous week to retire retroactive to July 2, 2010. He had been placed on administrative leave in June pending disciplinary review for improper handling of burial records, and was accused of botching dozen of contracts.
July 29, 2010 - Sen. Claire McCaskill, chairwoman of an oversight panel on the Senate Homeland Security and Government Reform Committee, says that her investigation of the cemetery has revealed between 4,900 and 6,600 graves may be unmarked or mislabeled on cemetery maps.
December 2010 - The Army launches the first criminal investigation into the misplacement of remains at Arlington National Cemetery after discovering the cremated remains of eight people dumped in a single grave site.
December 22, 2010 - President Barack Obama signs into law bill S. 3860, which will hold the Secretary of the Army accountable to Congress on Arlington National Cemetery's ability to identify and fix errors in the burial records for gravesites.
December 23, 2011 - According to the Army Inspector General's report, of the 259,978 graves audited, 195,748 were checked. The consequences were that in 64,230 cases, the information on the headstones was incorrect when they were compared to the paper or electronic records.
January 25, 2012 - During a congressional hearing on cemetery operations, investigators say that they have found no documentation accounting for $12 million that is missing from the cemetery's budget. The money was allocated to the cemetery between 2004 and 2010 but apparently was never spent.
January 26, 2012 - Former Marine Corps reservist Yonathan Melaku, is sentenced to 25 years in prison for attempting to desecrate graves at the Arlington Cemetery.
2012 - Arlington is seeking to be placed on the National Register as a historic "district." The entire process takes up to a year.
April 11, 2014 - The National Park Service lists the Arlington National Cemetery Historic District is listed on the National Register of Historic Places.
June 15, 2014 - The 150th anniversary of the cemetery.
Famous People Buried at Arlington:
President William Howard Taft
President John F. Kennedy and Jacqueline Bouvier Kennedy Onassis
Senators and brothers Robert F. and Edward M. Kennedy
Chief Justices Earl Warren, Warren Burger and William Rehnquist
General George C. Marshall
Margariette Higgins, Pulitzer Prize-winning war correspondent
Dashiell Hammett, author and veteran of both World War I and II
Spotswood Poles, baseball player in the Negro Leagues
Audie Murphy, actor and most decorated U.S. soldier of World War II
Glenn Miller, noted composer and Big Band leader, has a headstone as his body was never recovered after a plane crash in World War II.
James Parks, a former Arlington Estate slave and gravedigger, he is the only person buried in Arlington National Cemetery who was born on the property.
Anita Newcomb McGee, the first female Army surgeon and founder of the Army Nurse Corps
Walter Reed, pioneering bacteriologist
Astronauts Lt. Col. Virgil I. "Gus" Grissom and Lt. Cmdr. Roger B. Chaffee, killed at Cape Canaveral, Florida in a fire aboard their Apollo spacecraft. They are buried next to one another.
Sgt. Mark Matthews, the oldest of the Buffalo Soldiers, 111 years old in 2005
Medgar Evers, murdered civil rights leader
Thurgood Marshall, first African-American Supreme Court justice.
Joe Louis, former boxing Heavyweight Champion of the World
Lee Marvin, actor and World War II veteran
Pierre Charles L'Enfant, architect and designer of the city of Washington, D.C.