Economy after Mexican American war

Answer 1

A week after the Mexican-American war, gold was found in the newly annexed territory now called California. This sparked the gold rush which led to a massive expansion of the population and thus the development of California. As for the national economy, the gold found in the Mexican cession was used to fuel America's industry as investment money or it went to the government and expanded the national wealth.

Answer 2

The economy was on a roll.