Many of the firefighters wore full fire gear, including air tanks, and carried hoses and other tools as they made their way up and down the steps at the iconic concert venue today. That's the equivalent of climbing 110 stories — the height of the World Trade Center's Twin Towers.
There was also a ceremony at Fort Carson that included members of all the U.S. military services and representatives from other military bases near Colorado Springs.
It began with a prayer from Army chaplain Lieutenant Colonel Robert Glazener.
"I pray for the mothers, fathers, sons and daughters lost on Sept. 11, and the many more since that day ensuring that such a tragedy never happens again," he said.
U.S. Sen. Cory Gardner told those gathered the events of the day were a lesson for the country: "A lesson of great sacrifice, of heroic acts. Of people who were willing to give up their lives who would never be thanked by those who never got to tell them thank you."
In New York, the mournful playing of taps marked the conclusion of the World Trade Center ceremony marking the 14th anniversary of the attacks.
Linda Spinella, of Wayne, New Jersey, was there to honor her brother, Mark Zangrilli. The father of two worked for an insurance company in the south tower.
Spinella blinked back tears and said she doesn't like to think about what happened that day. Instead, she concentrates on the the happy memories, like her brother's "goofy jokes and the way he loved his kids."
Vice President Joe Biden and singer Billy Joel honored firefighters at a station whose ranks were decimated on 9/11. The two joined New York Gov. Andrew Cuomo in Manhattan at Rescue Company 1, a unit of the Fire Department of New York. Rescue 1 lost nearly half its members when it responded to the north tower of the World Trade Center.
Biden greeted firefighters with hugs and handshakes in front of memorial plaques honoring their comrades who died on 9/11 and in other incidents. He praised the firefighters for their loyalty and told them to take care of themselves. The vice president also planned to join Cuomo on Friday at the kickoff for the 9/11 Memorial Motorcycle Ride.
In Pennsylvania, the names of passengers and crew killed in the hijacking of United Flight 93 were read as bells also toll in their honor.
Hundreds gathered for a ceremony to honor the 33 passengers and seven crew members aboard the flight brought down near Shanksville, Pennsylvania.
Flight 93 was headed from Newark, New Jersey, to San Francisco when it was hijacked with the likely goal of crashing it into the White House or Capitol. A passenger revolt ended with it going down in a Pennsylvania field.
Ben Mecham of Johnstown, Pennsylvania, brought his 7-year-old son, Parker. He said children should not think of it as just "another plane crash."
Parker said he "can't believe" that people were so brave.
President Barack Obama said Friday he remembers sitting down on the evening of 9/11, rocking his baby daughter Sasha to sleep and sensing for the first time in his life that the U.S. homeland was vulnerable.
His recollections came as he spoke with service members at Fort Meade in Maryland.
Obama was a state senator in Illinois when the terror attacks occurred. He told the troops the destruction that day shows "just how precious what we have is and the need for us to defend it at any cost."
He also said he remembers and gives credit to President George W. Bush for going to the World Trade Center site and throwing out the first pitch at Yankee Stadium after the attacks. He recalled thinking as he watched that people are Americans first, not Republicans or Democrats, or Texans or Californians, and that they all had to unite for the country.
He told military service members he wanted to use the day to make sure those killed are never forgotten. He reassured the troops that the U.S. must work to make sure that the men and women in uniform have the strategy and resources they need to succeed.
Obama said the U.S. is still an indispensable force for good around the world, and added that the country still faces significant threats, including from the Islamic State group forces in the Middle East.
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