The Roosevelt River is a Brazilian river that originates in the state of Rondônia, and the only one named after a North American personality.
Along its course, it crosses a part of Mato Grosso, then enters the state of Amazonas, where it becomes a tributary of the Aripuanã River.
Initially, it was called the River of Doubt because nautical charts indicated the existence of a waterway connecting the headwaters of the Madeira tributary of the Amazon River with the Plata Basin. Thanks to an expedition at the beginning of the 20th century, its true course was discovered and the river was renamed the Roosevelt River.
The visit of then former US President Theodore Roosevelt to Brazil, in the so-called Rondon-Roosevelt Scientific Expedition, led by Marshal Cândido Rondon, was interesting for Brazil because, although the hypothetical fluvial passage to the Plata did not exist, it was discovered that the space between rivers was still a region nonexistent on Brazilian maps and, according to Euclides da Cunha’s calculations, corresponded to an area equivalent to the state of Rio Grande do Sul or Maranhão.
Today, the Roosevelt River is becoming a new tourist frontier, attracting visitors interested in exploring the river’s rapids (it is one of the most dangerous rivers in the world), practicing sport fishing, jungle lodging, among others.