Areas in the Colorado mountains, parts of north eastern Colorado and locations south of Colorado Springs were affected by the outage. The Front Range, from Colorado Springs north to Fort Collins, was not affected.
Affected cities in Colorado included Alamosa, Vail, Aspen, Durango and Grand Junction, while affected cities in Wyoming included Laramie, Casper and Cheyenne.
Verizon says parts of western Wyoming still have Verizon service.
An official with Verizon says it appears a switch, which routes wireless calls, failed around 2 a.m. Workers tried to fix the problem and said they hoped to have it fixed later in the day on Thursday.
The outage was affecting calls and text messages.
(KUSA-TV © 2010 Multimedia Holdings Corporation)