On September 11th, 2001, terrorists attacked the United States by hijacking commercial airliners and using them as guided bombs. Two planes crashed into the twin towers in NYC. Another plane crashed into the pentagon. The fourth hijacked plane, United Flight 93, never made it to its assumed destination of Washington DC.
Passengers and crew aboard Flight 93, fought to retake control of the plane. It crashed into a field, less than 30 minutes west of Bedford, PA.
From 2001 through 2010, there was a temporary memorial on the site, comprised of private memorials and tributes left there by private citizens.
Construction of a permanent memorial began in 2010 and the first phase of the project opened in September of 2011.