What was the first great leap for humans?

The constitution, Declaration of Independence, the mayflower in 1620 where less than half people survived the hrsh winter

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.