USA HISTORY

Detailed explanation-1: -Mexico claimed the Nueces River to be Texas’s southern border, but the United States insisted the border lay further south at the Rio Grande River. The Mexican-American War confirmed Texas’s southern border at the Rio Grande, indicating the United States victory.

Detailed explanation-2: -The immediate cause of the Mexican-American War was a disputed boundary between the United States and Texas on the Nueces Strip. Mexico did not recognize Texas as legitimate American territory and Texas admission to the United States antagonized Mexican officials and citizens.

Detailed explanation-3: -Expansionistic fervor propelled the United States to war against Mexico in 1846. The United States had long argued that the Rio Grande was the border between Mexico and the United States, and at the end of the Texas war for independence Santa Anna had been pressured to agree.

Detailed explanation-4: -The war and treaty extended the United States to the Pacific Ocean, and provided a bounty of ports, minerals, and natural resources for a growing country. The abundance of lands also produced debates about extending slavery into the West, a dispute that would help spark a nation-defining civil war.

Detailed explanation-5: -Reference to the Rio Grande boundary of Texas was omitted from the U.S. Congress’s annexation resolution to help secure passage after the annexation treaty failed in the Senate. President Polk claimed the Rio Grande boundary, and when Mexico sent forces over the Rio Grande, this provoked a dispute.