Area code 737

512 and 737 are North American telephone area codes serving Austin, Texas, and its suburbs. Counties currently served by these area codes include Bastrop, Burnet, Caldwell, Hays, Travis, Milam and Williamson.

Area code 512 was one of the original area codes established in October 1947. At the time, it covered most of the south-central portion of Texas, from the Gulf of Mexico to the Mexican border. Besides Austin, it included San Antonio, Corpus Christi, Brownsville, Harlingen, and McAllen.

Despite the presence of San Antonio and Austin—the state's third- and fourth-largest cities, respectively, for most of the second half of the 20th century—this configuration remained in place for 45 years. In 1992, the western part of its territory (including San Antonio and the Rio Grande Valley) was split off as area code 210, making 512 the last of Texas' original four area codes to be split. Typically, the largest city in an existing area code keeps the original code, which in this case would have been San Antonio. However, because of the wide dissemination of phone numbers for the plethora of state agencies in Austin, state regulators decided that having the Austin area keep 512 would be less disruptive.

On February 13, 1999, the 512 area code was reduced to its current size when the southern portion (including Corpus Christi) became 361.

To stave off exhaustion by the end of 2013, area code 737 was introduced as an overlay of 512 in July 2013. Ten-digit dialing within the 512 territory was phased in beginning December 2012 and made mandatory since June 2013.

...
Wikipedia