Cingular Preferred Nation Coverage Map for GSM Customers

T-Mobile National Coverage Map

Verizon America's Choice Map, Includes some CDMA Roaming on Other Carriers, and a lot of Analog Roaming on Verizon.

AT&T National Network (TDMA)

AT&T National GSM

Sprint PCS Nationwide Map

Nextel's Nationwide Map

B Side      A Side

PDF's of AMPS Nationwide Coverage (from FCC)
Now do you understand why you want a phone with AMPS capability?!