Area codes 541 and 458

North American area code 541 covers the majority of Oregon, except the northwest part of the state. Its service area includes the cities of Eugene, Springfield, Corvallis, Albany, Medford, Bend, Ashland, The Dalles, and Pendleton, as well as the coastal region from Lincoln County to the California border. It began its split from area code 503 on November 5, 1995, and finished June 30, 1996. It is overlaid with area code 458, effective February 10, 2010.

The 541 area code also is found in a small part of northern California in the northeast corner of Del Norte County through Frontier Communications; these numbers are 541-596-XXXX, which also serves the O'Brien, Oregon area of the Redwood Highway. This is one of the very few examples of an area code crossing a state line.

Area code 503 was used for the entire state of Oregon until November 5, 1995, when area code 541 began service. With that change, the northwest, and most heavily populated, corner of the state retained the 503 area code and the rest of the state moved to 541.

The Oregon Public Utility Commission approved a number overlay with area code 458 for the entire area, resulting in mandatory 10-digit dialing for that area. Oregon's other area code overlay (503/971) already had this requirement. Ten-digit dialing was phased in beginning in July 2009, becoming mandatory in January 2010. The first exchange to be issued in the 458 area code was 205 in Eugene in August 2011.

...
Wikipedia