Answer:
Texas cattle industry began in diamond-shaped area by the Rio Grande, the Gulf of Mexico, and the Nueces River to insure a food supply.
Step-by-step explanation:
The reason why the area between the Rio Grande and the Nueces River was chosen was because of its prairies. The cattle would be able to roam freely while grazing on the practically endless supply of grass. The availability of food - along with the climate of the region- made this area most favorable for raising cattle.