USA HISTORY

Detailed explanation-1: -Westward expansion began in earnest in 1803. Thomas Jefferson negotiated a treaty with France in which the United States paid France $15 million for the Louisiana Territory – 828, 000 square miles of land west of the Mississippi River – effectively doubling the size of the young nation.

Detailed explanation-2: -The first great expansion of the country came with the Louisiana Purchase of 1803, which doubled the country’s territory, although the southeastern border with Spanish Florida was the subject of much dispute until it and Spanish claims to the Oregon Country were ceded to the US in 1821.

Detailed explanation-3: -During the 1800s, the United States expanded westward, across the Mississippi River and eventually to the Pacific Ocean. These western lands, already inhabited for centuries, were purchased, won, and seized outright from Indian tribes and other nations.

Detailed explanation-4: -James Knox Polk was the 11th president of the United States of America (1845-1849). As President he oversaw the largest territorial expansion in American history-over a million square miles of land-acquired through a treaty with England and war with Mexico.