<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 documented 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 . </P>

How many miles is the border between united states and mexico