Pennies will buy you so little today that the concept of dividing them into even smaller change seems ludicrous. Not so back in 1786, when the U.S. Continental Congress approved the mill, describing it as the "lowest money of accompt, of which 1,000 shall be equal to the federal dollar." (The term comes from the Latin mille, meaning 1,000.) While the Federal Government never actually produced a coin worth one-tenth of a cent, some states and local governments issued mills made of such cheap materials as tin, aluminum, plastic or paper. By the 1960s, however, the coins had depreciated so much in value that their production was virtually abandoned.

Read why counting money can make you happier.