Constitutional FAQ Answer #60
Q60. "Where may I find additional information on the evolution of Article 1 — Section 8 (Powers of Congress)...and specifically, 'To coin money, regulate the value thereof, and of foreign coin, and fix the standard of weights and measures.'"
A. This was included because under the Articles of Confederation, the states were permitted to coin their own money, which led to, at the least, confusion (though the federal government was able to set the value of gold and silver). This is addressed, briefly, in the Federalist Papers, number 42. See also number 44 for an explanation of Article 1, Section 10, which expressly forbids the states from coining money or issuing paper money.