USSOUTHCOM traces its origins to 1903, when the first U.S. Marines arrived in Panama to protect the Panama Railroad connecting the Atlantic and Pacific Oceans across the narrow waist of the Panamanian Isthmus.

Today, USSOUTHCOM is the unified command responsible for all U.S. Military activities on the land mass of Latin America, south of Mexico; the waters adjacent to Central and South America; the Caribbean Sea, with its 13 island nations, European and U.S. territories; the Gulf of Mexico; and a portion of the Atlantic Ocean.