This is a broad category for people who were citizens of the Republic of Texas.
In OTL, the Republic of Texas seceded from Mexico and existed from March 2, 1836, to February 19, 1846, with only limited international recognition. In 1845, Texas was annexed by the United States on March 1 and admitted to the Union as a state on December 29. Oddly enough, the Republic was not formally dissolved until seven weeks after the admission.
Because the Republic of Texas had such a short span of existence, no adult was ever a lifelong citizen of it. Most founding Texans had been citizens of the United States and/or Mexico, and most erstwhile Texans in 1845 became citizens of the United States.
Harry Turtledove has created a few fictional versions of the Republic of Texas. The most prominent of these (and the only one to name any inhabitants) is the Second Republic of Texas which appears in In at the Death, the closing volume of the Southern Victory series. Texas citizens from that volume are listed here.
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