When I was growing up, the area code synonymous with the city of Houston and Southeast Texas since 1947 was 713. Ironically when the Los Angeles class attack sub the USS Houston was launched in 1975, it carried the hull number 713. .
But with the proliferation of fax machines, pagers, dedicated phone lines for home computers and cell phones in the rapidly growing Houston metro area threatening to exhaust the supply of phone numbers available, it just became a Houston area code in March 19, 1983 when the rest of Southeast Texas was assigned the 409 one. .
That bought time until November 2, 1996, when the Houston area suburbs outside Beltway 8 were assigned the 281 area code and they thought the exhausting the phone numbers problem was solved for a while .
Key words in that last sentence are 'they thought the problem was solved'.
Continued rapid growth in the Houston area and proliferation of cell and smartphones meant that on January 16, 1999, another area code had to be created by the Texas Public Utility Commission.
On that date the 832 overlay area code was created and the boundary between the 713 and 281 codes was erased. Mandatory ten digit calling was instituted in the Houston area on that date as well.
Now that we Houstonians were about to once again run out of numbers by September, on July 1 another overlay area code, 346 has been instituted.
With about 5 million people and counting in the Houston metro area, we'll see how long it takes before we pick up another area code.