President Barack Obama with former President George W. Bush commemorated the 10th anniversary of the terrorist attack that took place in New York City, Washington, D.C., and in Shanksville, Pa. on Sept. 11, 2001.

They, with their wives, First Lady Michelle Obama and former First Lady Barbara Bush, were joined by thousands who gathered on a clear Sunday morning to grieve where many lives were taken, and where the twin towers of the World Trade Center once stood. With security high and no traffic, there was a poignant silence where a decade ago the 110-story skyscrapers collapsed after being hit by airliners hijacked by Al-Qaida terrorists, sending a cloud over lower Manhattan.

Ten years have passed since a perfect blue sky morning turned into the blackest of nights, New York Mayor Michael R. Bloomberg said in opening the ceremony. Since then, we've lived in sunshine and in shadows.

Obama then read from Psalm 46: The nations raged, the kingdoms were moved. He uttered his voice. The earth melted. The Lord of Hosts is with us. The God of Jacob is our refuge. Come behold the works of the Lord who has made desolations in the Earth. He makes wars cease to the ends of the Earth.

Bush read an 1864 letter from Abraham Lincoln to Lydia Bixby, a widow in Massachusetts who was believed to have lost five sons in the Civil War, the nation's greatest internal crisis.

Services marking the worst terrorist attack on U.S. soil continued later Sunday morning when Obama laid commemorative wreaths in Shanksville, Pa., where United Airlines Flight 93 went down in a grassy field, killing 40 people, and in the afternnoon at the Pentagon, the U.S. Department of Defense's headquarters in Alexandria, Va./Washington, D.C., where a fouth hijacked plane struck, killing 125 people.

911 Anniversary
A single rose rests atop a list names inscribed around the North Pool of the 9/11 Memorial during the 10th anniversary ceremonies at the site of the World Trade Center REUTERS
911 Anniversary
A woman cries while looking at the names inscribed at the North Pool of the 9/11 Memorial during the 10th anniversary ceremonies at the World Trade Center site in New York, Sept. 11, 2011. REUTERS
Robert Peraza, who lost his son Robert David Peraza, pauses at his son039s name at the North Pool of the 911 Memorial during tenth anniversary ceremonies at the site of the World Trade Center in New York
Robert Peraza, who lost his son Robert David Peraza, pauses at his son's name at the North Pool of the 9/11 Memorial during tenth anniversary ceremonies at the site of the World Trade Center in New York, September 11, 2011. The 9/11 attacks changed life in the United States forever, but 10 years after the devastating hit, New Yorkers have learned to live in a more dangerous world and are ready to move on. REUTERS
Mourners touch the names of lost loved ones during ceremonies marking the 10th anniversary of the 911 attacks on the World Trade Center, in New York
Mourners touch the names of lost loved ones during ceremonies marking the 10th anniversary of the 9/11 attacks on the World Trade Center in New York, September 11, 2011. REUTERS
U.S. President Barack Obama embraces victims039 family members as first lady Michelle Obama stands by at the 911 Memorial during the tenth anniversary ceremonies at the World Trade Center site in New York
U.S. President Barack Obama (2nd R) embraces victims' family members as first lady Michelle Obama (R) stands by at the 9/11 Memorial during the tenth anniversary ceremonies at the World Trade Center site in New York, September 11, 2011. The 9/11 attacks changed life in the United States forever, but 10 years after the devastating hit, New Yorkers have learned to live in a more dangerous world and are ready to move on. REUTERS
Firefighters leave St. Patricks Cathedral with U.S. flags during ceremony to honor New York firefighters that were killed in 911 attacks on World Trade Center, in New York
Firefighters leave St. Patrick's Cathedral with U.S. flags during a ceremony to honor New York firefighters that were killed in the 9/11 attacks on the World Trade Center, in New York September 10, 2011. REUTERS
Women pass out U.S. Flags to passers-by during a ceremony marking the 10th anniversary of the 911 attacks on the World Trade Center in New York
Women pass out U.S. flags to passers-by in lower Manhattan during a ceremony marking the 10th anniversary of the 9/11 attacks on the World Trade Center in New York, September 11, 2011. REUTERS
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