Zero miles. The Rio Grande forms one of the borders of Texas (and the Texas stretch of the Rio is also the U.S.-Mexico border), so the north bank of the Rio Grande is part of the soil of Texas. Farther upstream, beyond El Paso, the Rio Grande also runs through New Mexico and part of Colorado.
There are several cities in Texas separated from Mexico by the Rio Grande River. From west to east: El Paso Presidio Langtry Del Rio Eagle Pass Laredo Zapata Rio Grande City McAllen Harlingen Brownsville el paso