The United States Dollar, referred to as USD, is the official currency of the United States and one of the most widely used currencies in the world. The U.S. dollar plays an important role in international trade, financial markets and the global economic system, affecting global economic operations. The following provides an in-depth look at the history, characteristics, usage, and international and domestic impact of the U.S. dollar. The history of the dollar The history of the dollar can be traced back to the American Revolutionary War at the end of the 18th century. At the time, the various forms of currency circulating throughout the United States led to economic chaos. In order to establish a unified monetary system, the U.S. government established the U.S. Mint in 1792 and began to mint unified coins. However, in the early 19th century, there were still multiple local currencies in the United States, leading to currency chaos. In 1862, the U.S. federal government issued the first banknotes, known as "greenback notes." These notes were originally used to raise funds to pay for Civil War expenses, but have since evolved into the primary form of currency in the United States. In 1913, the United States established the Federal Reserve System, which was responsible for issuing and managing U.S. dollars. Characteristic currency code of the US dollar: The currency code of the US dollar is USD, which is a code specified according to the international standard ISO 4217. Coins and banknotes: US dollar coins include denominations of 1 cent, 5 cents, 10 cents, 25 cents, 50 cents and 1 dollar, while banknotes come in 1 dollar, 5 dollars, 10 dollars, 20 dollars, 50 dollars U.S. dollars and $100 equal denominations. Designs and Elements: U.S. dollar coins and banknotes feature U.S. historical figures, national symbols, presidential portraits, important buildings and other cultural elements. Usage of the U.S. dollar The U.S. dollar is widely used in the United States for various economic transactions and daily consumption. It is used to pay for goods and services, pay wages, make investments and savings, etc. The U.S. dollar is the cornerstone of the U.S. economy and also plays an important role internationally. The international impact of the US dollar The US dollar is one of the world's major reserve currencies and is widely used in international trade and financial markets. Many countries store their foreign exchange reserves in U.S. dollars and conduct international trade settlements in U.S. dollars. In addition, the U.S. dollar also serves as the main currency for foreign exchange transactions and bond issuance internationally. The international status of the dollar allows the United States to influence the economic policies of other countries and global financial stability. However, the international status of the U.S. dollar also brings some challenges, including the possible impact of U.S. exchange rate fluctuations on the economies of other countries, and the possible impact of U.S. monetary policy on the stability of global financial markets. Challenges and Prospects of the U.S. Dollar The U.S. dollar faces challenges such as exchange rate fluctuations, inflation, and fiscal policies. These factors may have an impact on the U.S. economy and the international financial system. In addition, with the rise of other countries' currencies and changes in the international economic landscape, the international status of the U.S. dollar may also face changes. In short, as one of the most important currencies in the world, the US dollar plays an important role in the international and domestic economy. Its stability and changes will have a major impact on the global economy and financial markets, so the movement of the US dollar has attracted the attention of governments, central banks and investors.