In the aftermath of the 9/11 attacks, an impromptu memorial was set up on a hill at the Navy Annex, overlooking the Pentagon, where people came to pay respects and place tributes.

[4] One month after the attacks, 25,000 people attended a memorial service at the Pentagon for employees and family members; speakers included President George W. Bush and Secretary of Defense Donald Rumsfeld.

[8] A pentagonal[9] granite marker 4.5 feet (1.4 m) high,[10] the memorial honors the five people for whom no identifiable remains were found.

Of the six international finalists selected, all were designers: Jean Koeppel and Tom Kowalski, Mason Wickham and Edwin Zawadzki, Jacky Bowring, Shane Williamson, Michael Meredith, and Julie Beckman and Keith Kaseman.

[citation needed] A wall along the edge of the Memorial begins at a height of 3 inches (7.6 cm) and rises to a height of 71 inches (180 cm), the ages of the youngest and oldest victim of the attack,[14] and about 85 crepe myrtle trees are planted on the memorial grounds.

[16] Donations include $250,000 from American Forests towards planting trees at the memorial,[17] and $1 million from the government of Taiwan.

[22] It was opened to the public in a separate ceremony with a music performance by the Navy Band and the Sea Chanters Chorus.

[24] To commemorate the anniversary each year, an American flag is hung on the section of the Pentagon hit by Flight 77.

[citation needed] Anniversary events also include the America Supports You National Freedom Walk, which has been held on Sundays.

A smaller service is held at the memorial site for family and friends of victims killed at the Pentagon on 9/11.