Area code 713 was assigned to the southeastern part, from the Sabine River to the Brazos Valley.
On November 2, 1996, area code 713 was split, with most of Houston's suburbs switching to 281.
This was intended as a long-term solution, but rapid growth in demand for telephone services from the proliferation of pagers and cellphones required additional numbering resources within two years in both numbering plan areas.
On May 9, 2013, the Public Utility Commission of Texas (PUC) announced the addition of yet another code, 346, to the Houston overlay as of July 1, 2014.
[2] 621 was reserved a fourth overlay code; the PUC approved its implementation in 2023 and began on January 23, 2025.