Panama
was inhabited by several indigenous tribes prior to settlement by the Spanish in the 16th century. Panama broke away from Spain in 1821 and joined a union of Nueva Granada, Ecuador, and Venezuela named the Republic of Gran Colombia. When Gran Colombia dissolved in 1831, Panama and Nueva Granada remained joined, eventually becoming the Republic of Colombia. With the backing of the United States, Panama seceded from Colombia in 1903, allowing the Panama Canal to be built by the U.S. Army Corps of Engineers between 1904 and 1914. In 1977 an agreement was signed for the total transfer of the Canal from the United States to Panama by the end of the 20th century, which culminated on 31 December 1999.