Explored and settled by the Spanish in the 16th century, Panama broke with Spain in 1821 and joined a union of Colombia, Ecuador, and Venezuela, known today as the Republic of Gran Colombia. When the latter dissolved in 1830, Panama remained part of Colombia. With US backing, Panama seceded from Colombia in 1903. The Panama Canal was built by the US Army Corps of Engineers between 1904 and 1914. In addition, Costa Rica occupies a few small areas along the border.