Initially, it consisted of a horseshoe-shaped area that almost completely surrounded Houston, but in 2000 it was divided into three sections.
The counties served by area code 409 are Chambers, Galveston, Hardin, Jasper, Jefferson, Newton, Orange, Polk, Sabine, Trinity, and Tyler.
This includes the following cities and towns: Anahuac, Beaumont, Bevil Oaks, Bon Wier, Bridge City, Bronson, Brookeland, Buna, Burkeville, Call, China, Colmesneil, Deweyville, Doucette, Evadale, Fannett, Fred, Galveston, Gilchrist, Groves, Hamshire, Hankamer, Hemphill, High Island, Hillister, Hitchcock, Honey Island, Jamaica Beach, Jasper, Kirbyville, Kountze, La Marque, LaBelle, Lumberton, Mauriceville, Milam, Nederland, Newton, Nome, Orange, Orangefield, Pine Forest, Pinehurst, Pineland, Pinewood Estates, Port Arthur, Port Bolivar, Port Neches, Rose City, Rose Hill Acres, Sabine Pass, Santa Fe, Silsbee, Sour Lake, Spurger, Stowell, Taylor Landing, Texas City, Tiki Island, Vidor, Village Mills, Wallisville, Warren, West Orange, Wiergate, Wildwood, Winnie, and Woodville.
In 2020, 988 was designated nationwide as a dialing code for the National Suicide Prevention Lifeline, which created a conflict for exchanges that permit seven-digit dialing.
This area code was therefore scheduled to transition to ten-digit dialing by October 24, 2021.