Humboldt and Bonpland conclude their five-year expedition in 1804, having journeyed through every type of region in present Colombia, Ecuador, Mexico, and Peru, and collected an enormous amount of data on flora (about sixty thousand specimens), fauna, climate, astronomy, geology, and the Earth's geomagnetic field.

Off the coast of South America, Humboldt measured the temperature of ocean water and described the upwelling of cold water from below (once called the Humboldt Current but since named the Peru Current).

Humboldt has also conducted extensive ethnographic, historic, and linguistic research during the expedition.