What is the boundary established by the US government in regard to Texas?

The boundary established by the US government in regard to Texas is the Rio Grande River. This river serves as the primary international boundary between the United States and Mexico, particularly along the southwestern edge of Texas. The significance of the Rio Grande as a boundary can be traced back to the Treaty of Guadalupe Hidalgo in 1848, which concluded the Mexican-American War. This treaty defined the border between the two countries, designating the Rio Grande as the boundary from the Gulf of Mexico to the point where the river reaches the present-day border with New Mexico.

The other rivers mentioned do not serve as the international boundary between Texas and another country. The Nueces River, while historically significant and part of earlier boundary disputes, is not the established boundary recognized by the US government. The Trinity and Colorado Rivers are important waterways within Texas but have no role in defining the state's boundary with Mexico. Understanding these distinctions is crucial for comprehending Texas's historical and geographical context.