c) the Articles of Confederation
The Articles of Confederation became the first "law of the land" for the United States in 1781, 4 years after it was created. However, it was not very effective. In 1787 plans were made to revise it, but politicians decided to do away with the Articles, creating the US Constitution, instead.
The answer to you question
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The expansion of railroads created more ways for things such as general goods to be shipped elsewhere to buyers or companies. (Hope this helps a bit, sorry for such a short answer.)
Tony Stark and Captain America jk sorry.
The Union and Confederates
