Territorial Expansion and Effects

Proposes that slavery is banned in any land gained from Mexico
Needless to say this did not go over very well and split the parties along sectional lines
It passed in the House, but narrowly failed in the Senate.
Debate over whether Mexican acquisitions should enter as free or slave states remained a bitter and controversial topic, eventually becoming a cause of the Civil War.

From only 14,000 to 225,000
It attracted settlers from not only the USA, but also from miners in the Pacific Rim and South America.

This begins the California Gold Rush, which causes many people to move west.
About 80,000 people, known as Forty-Niners, came pursuing these "easy riches". It was nowhere near as easy as they expected. People who came to California as merchants, selling clothes, food, and other resources to the Forty-Niners, often made more money than the miners themselves.

USA Gains 1.2 million sq miles of land.
The Mexicans are angry, bitter, and humiliated and continue to be so for years.
Polk is also upset, because he wanted to obtain even more land, but the northern public would not support a longer war, so he couldn't.

There was much debate about whether California would enter as a free or slave state, since its constitution excluded both free and enslaved African Americans, and there was already a balanced number of free and slave states in the USA.

USA gains another 29,640 sq miles in southern Arizona and New Mexico.
The Americans buy this to facilitate the building of a railroad across the country.
The Annexation of Texas, the Treaty of Guadalupe and Hidalgo, and the Gadsden Purchase combined increased the size of the USA by about 1/3. Only the Louisiana purchase has ever added more territory in one shot.