What is the most important role of the Constitution

The Constitution has three main functions. First it creates a national government consisting of a legislative, an executive, and a judicial branch, with a system of checks and balances among the three branches. Second, it divides power between the federal government and the states.

Explanation:

The Constitution’s framework owes much to the history that led to its drafting.  The limitations placed on the federal government and each of its branches were a reaction to the tyranny of British rule, and especially the tyranny of the single monarch.  Yet the breadth of the national government’s powers were a correction to the weak government of the Articles of Confederation (the short lived system before the present constitution), that had proved incapable of forging the thirteen original states into one nation.

The steel industry made possible the expansion of railroads given that the tracks are made of steel. The railroad companies were the biggest customers of the steel industry because thousands of miles of steel track were laid to connect all areas of the United States.