"This has been an incredible journey that has changed lives," commission chairman John Reynolds said, choking back tears as he gaveled out the meeting. "That's what this place is for."
They crafted boundaries for a new national park. They launched an international design competition that drew more than 1,000 entries and hundreds of community participants to determine how to reshape and use the scarred landscape.
They met 40 times, cajoled donors (federal, state and private) to raise roughly $60 million, beat back criticism over the park's size and design, and oversaw the construction of the heart of the park.
"We were just a group of strangers coming together," said Calvin Wilson, whose brother-in-law Leroy Homer was first officer on Flight 93. "Passion moved this group."
Two presidents and four Pennsylvania governors have held office since Sept. 11, 2001 - all committed to seeing the park to completion. Two Pennsylvania legislators who helped propel the project, Sen. Arlen Specter and Rep. John Murtha, are gone.
Reynolds said he sees the memorial as a continuation of a story that started more than 225 years ago in Philadelphia.
"Just as Independence Hall commemorates the creation of the Constitution and the beginning of the nation, this is another step in telling that story," said Reynolds, a former deputy director of the National Park Service.
The meeting drew about 50 people, mainly reporters and supporters of the project.
Also attending were crew members of the Somerset, a new amphibious transport ship that will be commissioned March 1 in Philadelphia in honor of the victims and the site.
"Each and every day, we will honor the collective sacrifice in the face of adversity," the ship's commander, Thomas Dearborn, told commission members.
The transport ship will carry a piece of the Flight 93 landscape with it. Steel from an old drag line, used for coal mining, that lay abandoned in the field near the crash site was used for part of its bow. The 40 stars on the ship's seal commemorate the passengers and crew on the Newark-to-San Francisco flight.
As a group, they have been credited with fighting to overtake the hijackers and thwarting an attack on the U.S. Capitol on a day that Congress was in session.
The National Park Service's private fund-raising partner, the National Park Foundation, announced this week that it, too, had completed its mission, raising $40 million in private funds for the park.
But there are new chapters in the Flight 93 story. Later Tuesday afternoon, Interior Secretary Sally Jewell led a crowd of more than 100 people in the groundbreaking for the park's visitor center, slated to open in 2015.
Standing near a field of wildflowers just below the flight path of the jetliner, Jewell recalled the passengers and crew who gave their lives for their country. "That's a lesson children can learn," she said. "Make this world a better place."
Still waiting to be built - and funded - is the Tower of Voices, a 93-foot carillon that will contain 40 bells.
Patrick White, vice president of the Families of Flight 93 group, said his work will not be complete until the last bell on the tower is in place.
"I will continue to do it until we complete the Tower of Voices, and I hear the voices reflected through the chimes telling us, 'Now you can rest,' " said White, whose cousin Louis Nacke of New Hope was aboard the plane. "And then we turn it over to the peaceful people of the world."
Contact Amy Worden at 717-783-2594 or firstname.lastname@example.org or follow @inkamy on Twitter.