The US dollar is the official currency of the United States and is widely used as a reserve currency globally. The code for the US dollar is USD, but it is often simply written as $. History of the US Dollar: The dollar was introduced in 1792, replacing currencies like the pound sterling and the Spanish dollar. Early US coins resembled the Spanish dollar, and paper banknotes were introduced later, initially printed in a greenish color. The final design for the paper US dollar was established in the 1990s. The US Dollar and Interesting Facts: The name "dollar" comes from "Joahimstaler," named after a silver mine in Joachimsthal, Czech Republic. Over time, it was shortened to "Taler" and then "Dollar." The slang term "Buck" comes from "buckskin," a key trading currency with Native Americans. Other countries, such as the British Virgin Islands, Ecuador, Panama, and El Salvador, also use the US dollar as their official currency.