The country that shares a border with the United States to the south is Mexico. This extensive border stretches approximately 1,954 miles and is defined by both natural features and urban areas. The U.S.-Mexico border is significant both geographically and economically, facilitating trade, cultural exchange, and migration. Major crossings include cities like San Diego and Tijuana, and the border region is marked by diverse landscapes ranging from deserts to rivers. The relationship between the two countries is complex, involving issues related to immigration, trade agreements, and security.