In 1851 William Lewis Herndon, through his cousin, Matthew Fontaine Maury and his connections, was ordered to head an expedition exploring the Valley of the Amazon -- a vast uncharted area. Departing Lima, Peru, 21 May 1851, Lieut. Herndon, Lieut. Lardner Gibbon, and a small party of six men pressed into the wild and treacherously beautiful jungles. They split up and took different routes to gather even more information on this vast area. After a remarkable journey of 4,366 dangerous miles, which took Herndon through wilderness from sea level to heights of 16,199 feet, Herndon reached the city of Pará, Brazil on 11 April 1852. On 26 January 1853 Herndon submitted an encyclopedic and profusely illustrated 414-page report to the Secretary of the Navy John P. Kennedy. The report was later published as Exploration of the Valley of the Amazon.

The two volumes, one written by Lieutenant Herndon and the other by Lieutenant Gibbon, were so unusual at that time and of such importance that in an unusual move, it was immediately ordered, "10,000 additional copies be printed for the use of the Senate." Three months later another 20,000 copies were ordered; the book became an international best-seller.

Their orders were to report on all possible conditions in the Amazon region that they would each have to traverse alone from Lima, Peru on the Pacific coast to Para, Brazil, the mouth of the Amazon. The two volumes were published by presidential order.