The document summarizes the construction and events of September 11, 2001 involving the Twin Towers of the World Trade Center in New York City. It describes the towers being built between 1966-1973 at a cost of $1.5 billion. On September 11, 2001, two planes hijacked by Muslim terrorists crashed into the towers, resulting in their collapse and killing nearly 3000 people. The attacks marked a pivotal moment that changed national security for the United States.