Amazon river dolphin widespread river dolphins. They are present in six countries in South America: Bolivia, Brazil, Colombia, Ecuador, Peru, and Venezuela, in an area covering about . The boundaries are set by waterfalls, such as the Xingu and Tapajós rivers in Brazil, as well as very shallow water. A series of rapids and waterfalls in the Madeira River have isolated one population, recognized as the subspecies "I. g. boliviensis", in the southern part of the Amazon basin in Bolivia. They are also distributed in the basin of the Orinoco River, except the Caroni River and the upper Caura River in Venezuela. The
American River of the Lakes) which may or may not have been an error, as in those times the area of the Central Valley surrounding the American River was home to vast marshes, which would have given the river the appearance of a series of lakes. During the 1820s, Jedediah Smith led an expedition to the American River with the goal of finding a safe route across the Sierra Nevada. After a failed attempt to cross the mountains via the South Fork of the American River, Smith's group managed to cross via Ebbetts Pass on the headwaters of the Stanislaus River, becoming