Peregrine Falcons were an endangered species until 1999 when they made a sufficient enough comeback to be removed from the list. Pennsylvania still considers the birds endangered and protects them (yeah PA). The birds almost became extinct due to pesticides like DDT causing their egg shells to become too thin and they would crack during incubation. These birds of prey can be found in large cities in the United States and prefer to nest on cathedrals, skyscrapers and towers of suspension bridges.
The Cathedral of Learning is part of the University of Pittsburgh campus in the Oakland section of the city and is a 42-story classroom tower (535 feet). The Gulf Tower is located downtown Pittsburgh and has 44 stories (582 feet).
To watch the falcons click here:
http://www.aviary.org/cons/falconcam_cl.php Cathedral of Learning
http://www.aviary.org/cons/falconcam_gt.php Gulf Tower