<Tr> <Th> Treaties </Th> <Td> Adams--Onís Treaty, Treaty of Limits (Mexico--United States), Treaty of Guadalupe Hidalgo, Gadsden Purchase </Td> </Tr> <P> The Mexico--United States border is an international border separating Mexico and the United States, extending from the Pacific Ocean to the west and Gulf of Mexico to the east . The border traverses a variety of terrains, ranging from major urban areas to uninhabitable deserts . Approximately 350 million legal crossings occur annually, and is the most frequently crossed border in the world . </P> <P> The total length of the continental border is 1,954 miles (3,145 km). From the Gulf of Mexico, it follows the course of the Rio Grande (Río Bravo del Norte) to the border crossing at Ciudad Juárez, Chihuahua, and El Paso, Texas . Westward from El Paso--Juárez, it crosses vast tracts of the Chihuahuan and Sonoran deserts to the Colorado River Delta and San Diego--Tijuana, before reaching the Pacific Ocean . </P> <P> Along this border are 23 U.S. counties and 39 Mexican municipalities, as well as a dramatic population increase . The main factors contributing to population rise are a significant increase in migrations, increase in the number of employment opportunities along the border region in Mexico, and the increase in the number of people illegally crossing the border into the United States in order to find better jobs and living standards . This border also plays a significant role in economic development on both sides and has negative and positive impacts on economic aspects when there is a change in populations or policies . This border also serves as the hub for trade and the exchange of goods . Mutual trade and exchange of goods make both countries depend on each other . Therefore, if one country, for example, faces economic issues, the other will also be affected by a decrease in employment opportunities . Although they may be mutually dependent on trade and economic development, both countries operate on distinct sets on governance, legal, economic, and social systems . This border defines the sovereignty of both countries . </P>

How long is the border of us and mexico