(Shanksville) -- The President and First Lady joined more than four thousand people at the Flight 93 National Memorial shortly after the commemorative service of the September 11th terrorist attacks. President Obama and First Lady Michelle Obama set a wreath at the memorial’s white marble wall bearing the names of the 40 passengers and crew of Flight 93 who died trying to take the cockpit of their plane from four terrorist hijackers aboard. Former Governor Tom Ridge says nine-eleven began a new chapter in American history and national security, but the heroic actions of those who died on Flight 93 shine through. "Tragedies teach us but they do not stop us. We are still the freest most blessed nation in this treasured world. And we will long honor that role with the memory and guidance of 40 good shepherds." Ridge was among several speakers at the commemoration, including Governor Corbett and local members of Congress Bill Shuster and Mark Critz, whose district includes the Flight 93 crash site. Before the morning ceremony began, the crowd assembling to watch had a moment of silence for each one of the planes that flew into the World Trade Center towers and the Pentagon.