Question

Before President Polk’s term, which river had the U.S. government recognized as the border between Mexico and Texas? Which river did Texas claim as its border with Mexico? Which river did Polk choose as the border? How did Polk’s choice of the border allow the United States to provoke a war with Mexico?

Answer 1

Before Polk, the United States and Mexico had boundaries along the Rio Grande River. Texas and Polk claimed that America's southern border ran down to the river south of the United States' positon back then. They had a war, but Mexico lost and U.S kept expanding.
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