What was the most important social event from 1848-1877?

It Was The Civil War and Reconstruction, 1848-1877 It lasted 15 weeks 

The transcontinental railroad provided a means of fast transportation. it cut a 6 month trip into 6 days, created jobs for many people and encouraged immigration. the homestead act played a huge role in western expansion; it allowed settlers to begin a fresh start, and gave them land in exchange for their residence for up to five years and a small fee.