The map above is linked from VerizonWireless Website. This is their national access map.
Areas in red are roaming, but both voice and data coverage should work without additional fees.
Please see the Verizon Wireless website for additional information. http://www.verizonwireless.com

Notes: A Verizon phone can make and receive calls in most areas where any other provider can make or receive calls, so their coverage area through roaming partners is actually much larger than that shown above. Verizon's AC plan now includes roaming in most of Oregon without any fees! Verizon is very nearly all digital in many places in the west.