The expedition was jointly led by Theodore Roosevelt, the former president of the United States, and Colonel Cândido Rondon, a Brazilian explorer who had discovered its headwaters in 1909.

[1] After losing a bid for a third presidential term in the 1912 election, Roosevelt had originally planned to go on a speaking tour of Argentina and Brazil, followed by a cruise of the Amazon River organized by his friend Father John Augustine Zahm.

[citation needed] The remaining party – the Roosevelts, Colonel Rondon, American naturalist George Kruck Cherrie, and 15 Brazilian porters (camaradas) – then started down the River of Doubt.

Insects and disease such as malaria weighed heavily on just about every member of the expedition, leaving them in a constant state of sickness, festering wounds and high fevers.

[2] By the time the expedition had made it only about one-quarter of the way down the river, they were physically exhausted and sick from starvation, disease, and the constant labor of hauling canoes around rapids.

The expedition was reunited on April 26, 1914, with a Brazilian and American relief party led by Lieutenant Antonio Pyrineus, an officer from Rondon's Telegraph Commission.

[4] To finally settle the dispute, in 1927 British explorer George Miller Dyott led a second trip down the river, confirming Roosevelt's discoveries.

[6] The expedition consisted of a total of twenty persons including Roosevelt's great-grandson Tweed Roosevelt, professional river guides Joe Willie Jones, Kelley Kalafatich, Jim Slade, and Mike Boyle, photographers Carr Clifton and Mark Greenberg, cinematographer Joe Kaminsky, Haskell's son Charles 'Chip' Haskell Jr. who served as the expedition's communications expert, Brazilian scientists Geraldo Mendes dos Santos and João Ferraz (ichthyologist and pharmacologist), chiefs Oita Mina and Tatataré of the Cinta Larga tribe whose land borders much of the river, and the journalist Sam Moses, who was contracted to write a book which was not published because Haskell and McKnight declined to approve the manuscript.

[7] A documentary of the expedition was subsequently produced and aired on PBS called the New Explorers: The River of Doubt narrated by Bill Kurtis and Wilford Brimley.