At one time prior to the Federal Reserve Act of 1913 there were around 150 different currencies in use in the US. Each of those had a different value against gold and the US dollar. Most were issued by banks or mining companies, but they made trade between states almost impossible, especially since they were well known to fail regularly.

Mandating that only US dollars could be used to pay a federal tax obligation provided the driving factor to allow the dollar to obsolete those other currencies and unify trade across states while also adding stability to the western states' economies.