Praxis II Elementary Education Social Studies (5904) Practice Test

The event behind this question is about how territorial expansion and disputed borders can lead to war. When Texas, which had been an independent republic after its revolution from Mexico, was annexed by the United States in 1845, Mexico still claimed Texas as its territory. This move intensified tensions because Mexico viewed the annexation as a direct challenge to its sovereignty and an act of American expansionism.

A key issue became the boundary between the two nations. Mexico said the border was the Nueces River; the United States claimed the Rio Grande as the boundary. Clashes in the disputed border area followed, and war broke out in 1846 as fighting escalated between Mexican forces and U.S. troops.

Other options don’t fit as the primary trigger: the Gadsden Purchase occurred later and was about acquiring land for a railroad route; the Louisiana Purchase happened much earlier and involved land not at the Texas-Mexico border; the Civil War occurred decades later and involved different conflicts.