Area code 587 is a telephonearea code that covers all of Alberta, Canada, in addition to the incumbent codes, 403 and 780. Numbers in this area code started being allocated in late 2008.
Prior to 1997, Area code 403 encompassed the province of Alberta, the Yukon Territory and the region that currently defines the Northwest Territories as well as a very small western portion of what is today the territory of Nunavut (which split off form the Northwest Territories on April 1, 1999). However, in 1997, 403 began exclusively serving Alberta, with all other portions of 403 (as well as the portion of Area code 819 that had served the region which is today's Nunavut but which, at the time, was still a part of the Northwest Territories) splitting off into a new Area code 867. In January 1999, the northern two-thirds of Alberta, including Edmonton, split off as 780, leaving 403 to serve Calgary and southern Alberta. The projected exhaust date for area codes 403 and 780 was March and October 2009, respectively. In 1997, two area codes, 587 and 825, were reserved for Alberta's use by Bellcore. The new area code overlays 403 and 780 simultaneously, covering the entire province, and made 10-digit dialing necessary. This was implemented in order to spare rural Albertans the burden of having to change their numbers.
As a preliminary step, optional ten-digit dialling was introduced across the province on 23 June 2008 and became mandatory on 12 September 2008. On 20 September 2008, Telus Mobility began allocating numbers starting with area code 587 in the Calgary area.