Patent and Trademark Depository Library (PTDL)

a library designated by the USPTO to receive copies of patents, CD-ROMs containing registered and pending marks, and patent and trademark materials that are made available to the public for free. As of October 1st, 2011 these libraries have been renamed and are referred to as Patent and Trademark Resource Centers (PTRCs). The term “PDTL” is no longer used.

— see PTRC for a list of locations and more info