USA HISTORY

Detailed explanation-1: -Texas used the Adams-Onís as a boundary line to the U.S., but decided to set the Rio Grande (called the Río Bravo del Norte in Mexico) as its boundary line to Mexico.

Detailed explanation-2: -Texas claimed the Rio Grande as its southern border. Mexico said the Nueces River, to the north, should be the border.

Detailed explanation-3: -The Rio Grande serves as the border here. “The Rio Grande is a natural border, has been since 1848, and the ties between cities and towns on either side are strong, ” CNN’s Gregory Krieg reported.

Detailed explanation-4: -Mexico did not recognize Texas as legitimate American territory and Texas admission to the United States antagonized Mexican officials and citizens. Rather than ameliorate this problem, President Polk intentionally worked to aggravate Mexico and provoke a war.