Try plugging in the approach/departure frequencies for Philadelphia Int'l, Dulles Int'l, Reagan Int'l, and Harrisburg, along with NY ARTCC, and ZDC ARTCC. With the right antenna, you should be able to hear any one of those. When I stayed in Gettysburg I as able to hear at least one frequencies from all of the above categories. The distance you can hear aircraft all depends on the aircraft altitude, antenna height and terrain. On good days I can hear aircraft transiting ZNY's KENNEDY sector. You should be able to pick up the ground side comms from a couple ZNY (NY ARTCC) frequencies also. You should have tons to listen to in Lancaster! Good luck!
