What major event occurred in 1821?

Mexico won its independence from Spain.

Explanation:

The leaders of Mexico and the United States met to talk about American settlers moving into the area of Texas.

in 1803 the louisiana purchase took place, doubling the size of the country. by 1840 almost 7 million americans had migrated westward in hopes of securing land and being prosperous. the belief that settlers were destined to expand to the west is often referred to as manifest destiny.

explanation:

it was on the rise and doing very well and would continue to do well until the great depression from 1929-1939