Texas Civil Practice and Remedies Code - CIV PRAC & REM § 21.021. Application

(1) is part of two or more judicial districts, that has two or more district courts with regular terms, and that is part of a district in which a county borders on the international boundary of the United States and the Republic of Mexico;

(2) borders on the international boundary of the United States and the Republic of Mexico and that is in a judicial district composed of four counties;

(3) borders on the international boundary of the United States and the Republic of Mexico and that has three or more district courts or judicial districts wholly within the county;  or

(4) borders on the Gulf of Mexico and that has four or more district courts or judicial districts of which two or more courts or districts are wholly within the county.