What led to the writing of the constitution?

It was primarily the failure of the Articles of Confederation to deal with the issues arising between the states that led to the writing of the Constitution, since it was clear there needed to be a "stronger" central government. 

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.