Why is a dime smaller than a penny? A penny, nickel, quarter, half dollar, and silver dollar are each progressively larger. The dime is out of sequence! This is definitely driving me nuts!
-- Al, San Diego
Once upon a time, we New World colonists used a lot of screwy things for legal tender. For example, in Virginia you could pay for things with tobacco, but money that anyone could grow freely in his back yard had obvious drawbacks. So the Constitution reserved for the feds the right to create money. Coins at that time were struck from nearly pure metal-- copper, silver, or gold. And the size of the coin reflected its value in that metal. E.g., a gold eagle was bigger, therefore contained more gold, therefore was of greater value than a half eagle or a quarter eagle. Same for copper and silver coins. (The number of grains of the pure metal was specified by law.) Since pennies were made of copper and dimes made of silver, their sizes would have been unrelated to one another, only to other copper or silver coins.