The U.S. dollar is the most widely used currency in the world today. No wonder the printing presses at the U.S. bureau of Engraving and Printing in Washington, D.C. run 24 hours a day!

All the nation's paper money is printed in Washinton, D.C. In 24 hours, the bureau can print ten million one dollar bills.

The bills are sent to one of 12 regional Federal Reserve Banks, which distribute the dollars to banks, where they go out into circulation to be used everywhere.

Just a Cookie Cutter
Coins are ade at four "mints" in the USA. Pennies are made of a copper-coated zinc alloy (an alloy is a mixture). Nickels are a mixture of copper and nickel. Dimes, quarters, half dollars and dollars have a copper core covered with an alloy of copper and nickel.

A machine cuts out blank coins from a thin sheet of metal, the same way a cookie cutter works. Ridges are put around the edges of quarters and dimes. The design is pounded into the coins.

A Fort Full of Gold
Until the mid-1800s the banks, not the government, printed money. Paper money was called a bank note - it was a promise that the bank would exchange the bill for gold or silver. But sometimes the bank didn't keep its promise. So in 1861, the U.S. government began printing paper money.

Years ago, U.S. dollars were gold-backed, which meant that you could exchange paper money for gold at your bank. That's no longer true, but the government still keeps a vast storehouse of gold in the Unites States Gold Bullion Depository at Fort Knox in Kentucky. It's protected by guards armed with machine guns and it's stored in concrete and steel vaults inside a bomb-proof building.