Area codes 503 and 971
Despite Oregon's dramatic growth in the second half of the 20th century, particularly in the Willamette Valley (Portland and Eugene), 503 remained Oregon's sole area code for 48 years, making Oregon one of the largest states with just one area code. However, by the early 1990s, 503 was on the brink of exhaustion due to the proliferation of cell phones and pagers, particularly in the Portland area. The supply of numbers was further limited because Oregon is split between several LATAs that spill into neighboring states. The Portland LATA extends into southwestern Washington, while Malheur County is part of the Boise/southern Idaho LATA and the Spokane, Washington LATA extends into northeastern Oregon.
This was intended as a long-term solution. However, the Portland area is home to the great majority of Oregon's landlines, as well as most of its cell phones and pagers. Additionally, the Portland LATA spills into southwestern Washington and also includes much of eastern Oregon, meaning several numbers in 541 and Washington's area code 360 weren't available for use. As a result, 503 was on the brink of exhaustion again within only three years.
On July 1, 1999, area code 971 was created as a concentrated overlay for most of the 503 territory, with the exceptions of Clatsop and Tillamook counties. Initially, 10-digit dialing was to become mandatory in that service area on January 30, 2000, but the date was extended until October 1, 2000.
The previously exempted Clatsop and Tillamook counties were added to the 503/971 overlay on April 27, 2008.
Area codes 503 and 971 include communities in the following counties:
- "Area Code History". Retrieved May 25, 2012.
- "Split of 503 (Oregon) Numbering Plan Area (NPA)" (PDF). North American Numbering Plan Administration. May 19, 1995. Retrieved May 25, 2012.
- "Concentrated Overlay of 503 Numbering Plan Area (NPA) with 971 NPA" (PDF). North American Numbering Plan Administration. July 21, 1999. Retrieved May 25, 2012.
- "Permissive Dialing Extended for the 503/971 Concentrated Overlay (Oregon)" (PDF). North American Numbering Plan Administration. December 10, 1999. Retrieved May 25, 2012.
- "Expansion of the Concentrated NPA 971 Overlay with NPA 503 (Oregon)" (PDF). North American Numbering Plan Administration. December 21, 2006. Retrieved May 25, 2012.