Final answer:
The Treaty of Guadalupe Hidalgo is significant because it expanded the borders of the United States and ended the Mexican-American War. It included a large territory that later became part of several U.S. states and embodied the idea of Manifest Destiny.
Step-by-step explanation:
The Treaty of Guadalupe Hidalgo is important in U.S. History because it Option B: It expanded the borders of the United States. This treaty, signed in February 1848, ended the Mexican-American War by confirming U.S. title to Texas and ceding the Alta California and New Mexico territories, accounting for some 525,000 square miles. Mexico was left with territories south of the Rio Grande, while the U.S. committed to paying $15 million and assuming American claims against Mexico, totaling approximately $3,250,000.
The land acquired became, wholly or in part, the states of California, Arizona, New Mexico, Texas, Utah, Nevada, Colorado, Wyoming, and Kansas. This significant expansion supported the concept of Manifest Destiny, representing the belief that the U.S. was destined to expand across North America. The transfer of this vast territory was a transformative event that shaped the political, social, and geographic landscape of the United States.