Across the United States, people are paying tribute to those who died while serving their country.

The Memorial Day holiday is observed on the last Monday in May.

The three-day weekend also serves as sort of an unofficial start to the summer season. Many people take advantage of the holiday to travel and enjoy the outdoors.

The sunrise silhouettes the US Marine Corps War Memorial in Arlington, Virginia, on Monday, May 30.
The sunrise silhouettes the US Marine Corps War Memorial in Arlington, Virginia, on Monday, May 30.
J. David Ake/AP
President Joe Biden lays a wreath at The Tomb of the Unknown Soldier during ceremonies Monday at Arlington National Cemetery.
President Joe Biden lays a wreath at The Tomb of the Unknown Soldier during ceremonies Monday at Arlington National Cemetery.
Andrew Harnik/AP
Military personnel unroll a 100-foot American flag during the Intrepid Sea, Air & Space Museum's annual Memorial Day Commemoration Ceremony in New York on Monday.
Military personnel unroll a 100-foot American flag during the Intrepid Sea, Air & Space Museum's annual Memorial Day Commemoration Ceremony in New York on Monday.
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Christopher Gomes places American flags at the graves of veterans buried at the Pine Grove Cemetery in New Bedford, Massachusetts, on Sunday. Gomes, an Army veteran, lost his right leg in 2008 while serving in Iraq.
Christopher Gomes places American flags at the graves of veterans buried at the Pine Grove Cemetery in New Bedford, Massachusetts, on Sunday. Gomes, an Army veteran, lost his right leg in 2008 while serving in Iraq.
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Participants in the Rolling to Remember event touch a veteran's name at the Vietnam Veterans Memorial in Washington, DC.
Participants in the Rolling to Remember event touch a veteran's name at the Vietnam Veterans Memorial in Washington, DC.
Stefani Reynolds/AFP/Getty Images
US veterans and their relatives pray during the Remembering our Fallen Exile Deported Veterans event at the US-Mexico border in Playas de Tijuana, Mexico, on Sunday, May 29.
US veterans and their relatives pray during the Remembering our Fallen Exile Deported Veterans event at the US-Mexico border in Playas de Tijuana, Mexico, on Sunday, May 29.
Guillermo Arias/AFP/Getty Images
Fireworks explode over the Philadelphia skyline as part of Memorial Day celebrations on Saturday, May 28.
Fireworks explode over the Philadelphia skyline as part of Memorial Day celebrations on Saturday, May 28.
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Members of the US Air Force Honor Guard drill team perform in Miami Beach, Florida, on Saturday.
Members of the US Air Force Honor Guard drill team perform in Miami Beach, Florida, on Saturday.
Cristobal Herrera-Ulashkevich/EPA-EFE/Shutterstock
People salute during the Rolling to Remember event in Washington, DC, on Saturday.
People salute during the Rolling to Remember event in Washington, DC, on Saturday.
Stefani Reynolds/AFP/Getty Images
Guests place flowers Saturday at the Tomb of the Unknown Soldier in Arlington National Cemetery.
Guests place flowers Saturday at the Tomb of the Unknown Soldier in Arlington National Cemetery.
Tasos Katopodis/Getty Images
The Washington Monument is seen behind a person saluting during a Memorial Day event on Saturday.
The Washington Monument is seen behind a person saluting during a Memorial Day event on Saturday.
Stefani Reynolds/AFP/Getty Images
A member of the US Army's 3rd US Infantry Regiment places flags at Arlington National Cemetery on Thursday, May 26.
A member of the US Army's 3rd US Infantry Regiment places flags at Arlington National Cemetery on Thursday, May 26.
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People look at the Vietnam Veterans Memorial in Washington, DC.
People look at the Vietnam Veterans Memorial in Washington, DC.
Stefani Reynolds/AFP/Getty Images