The United States, 1850

By bluffing war, the British were convinced to accept the border at the 49th parallel. North of the line would become British Columbia. South of the line would become Oregon, Washington and Idaho.

At the same time president James K. Polk sent diplomats to Mexico to persuade them to sell California and New Mexico. The Mexicans refused, some demanding that they should receive compensation for the loss of Texas before any more territory was ceded.

Polk then sent General Zachary Taylor into the region disputed between Mexico and the United States. After a brief border skirmish, Polk declared to Congress that Mexico had "invaded our territory and shed American blood upon the American soil." Congress approved the declaration of war upon the United Mexican States.

The US won victory after victory. Eventually they landed a force at Veracruz to march on the capitol. By Sept 15, 1847 The US Army marched into Mexico City.

With US victory, Mexico signed the Treaty of Guadalupe Hidalgo, ceding to the US its California and New Mexico territories in exchange for $15 million dollars. The treaty was signed February 2, 1848.

On Jan 24, 1848 gold was discovered in California. California would become a state virtually overnight.

--American History Map Series--

1790 [link]
1802 [link]
1804 [link]
1819 [link]
1823 [link]
1837 [link]
1846 [link]
1850
1862 [link]
1900 [link]

Original map base courtesy of Wikipedia

2/19/12 EDIT:
map base source [link]
map base created by Lokal_Profil [link]