San Antonio's one ZIP code that isn't in Bexar County
USPS lists 83 ZIP codes with San Antonio as the primary place name, fourth-most of any Texas city behind Houston, El Paso, and Dallas, as this site's Texas ZIP code overview breaks down. 82 of those 83 sit inside Bexar County. The one exception is 78266, a ZIP in San Antonio's far northeast corner that also covers the small cities of Garden Ridge and Selma; most of that ZIP falls in Comal County, the county just northeast of Bexar that's home to New Braunfels. That's a real border crossing showing up right in a San Antonio ZIP code, a step further than what Houston and Dallas have, where annexation has pulled the actual city limits into neighboring counties without any of it touching a ZIP code.
Bexar County's territory once reached toward Wyoming
Bexar County predates Texas independence by name. It takes its name from San Antonio de Béxar, the municipality Spain established at the site in 1731 after 16 families of Canary Islanders, 56 settlers in all, arrived and set up next to the mission system already there. When the Republic of Texas organized Bexar as a county on December 20, 1836, with San Antonio as its seat, the county covered almost the entire western half of the republic, including disputed territory stretching through eastern New Mexico and north toward Wyoming. That footprint didn't last. Texas began partitioning Bexar's territory in 1860, and by the time the process wrapped up, 128 of the state's 254 counties had been carved out of the original county, according to the Texas State Historical Association's Handbook of Texas. What's left, at 1,248 square miles, still ranks as Texas's fourth-largest county by population today, behind Harris County (Houston's home county), Dallas, and Tarrant (Fort Worth). The Census Bureau's latest estimate puts Bexar at roughly 2.16 million residents, up from just over 2 million at the 2020 census.