When you come to Philadelphia, please don't miss the American Mint. Since the United States opened its ports, the vast majority of the currencies in circulation in the United States have been made here. The production line here is unavoidably displayed to the public, but photographs are not allowed inside. Visit the line in the upper layer of the factory, all glass windows, clearly see the factory's production line, can not see the inside of the machine, it does not matter, many electronic touch screens are in front of you, want to see which part, click on the screen, pop up video or pictures. There are also touching areas for each coin, with projection and coin pop-up. Appreciate the undisguised and generous style of the United States.