A term derived from the 19th-century definition of The Tropics, Central and South America. However, the term has come to mean a broader geographical area, which is the region that lies between 23 1/2 degrees north and south latitudes known as the Torrid Zone. Included are the regions of Africa and the South Pacific as well as South America. 19th-Century North American artists began exploring South America as expedition artists in the 1830s. It was a time of Expansionism and Manifest Destiny, and South American exploration was encouraged by the German naturalist, Alexander von Humboldt. The idea grew that because North and South America shared a geographical unity, South America was well worth visiting by North American artists. Many of them were intrigued by the lush landscape, and among artists linked to 19th century Tropical Landscape painting are Frederick Catherwood, Norton Bush, Martin Johnson Heade, Jacques Burkhardt, George Catlin, Frederick Church, Titian Peale, and James Whistler. Source: Katherine Emma Manthorne, "Tropical Renaissance: North American Artists Exploring Latin America".