A district may be created by order of the commissioners court of each county located on the Texas-Mexico border that has a population of:
(1) 500,000 or more and is adjacent to two or more counties each of which has a population of 50,000 or more;
(2) 350,000 or more and is adjacent to a county described by Subdivision (1); or
(3) less than 300,000 and contains one or more municipalities with a population of 200,000 or more.