The American Expedition (1799–1804) was a scientific exploration of Spanish America conducted by the Prussian naturalist Alexander von Humboldt and the French botanist Aimé Bonpland. Over the course of five years, the expedition traversed across present-day Venezuela, Colombia, Ecuador, Peru, Cuba, Mexico, and parts of the United States. Humboldt and Bonpland conducted pioneering research in fields including geography, biology, geology, meteorology, and ethnography.
They observed and described vast regions of South and Central America, mapping rivers like the Orinoco and investigating the Andes Mountains—including an attempt to climb Chimborazo, accompanied by local savants and informants. Their observations of plant and animal life, atmospheric phenomena, and indigenous cultures - influenced by the debates ongoing in Spanish American in those years - laid the foundations for modern biogeography and ecology.
Background By the mid-1790s, Humboldt had devoted himself wholly to scientific investigations. Despite being offered a promotion and an increase in pay, he resigned his position as a mining official in the Prussian civil service in order to embark on a journey that would “advance him scientifically.” To the Minister of Mines in Berlin Humboldt declared: "I am considering a complete change in my mode of life, and I intend to withdraw from any official position with the state." His health, he claimed, had suffered. All he had wanted was to prepare himself for a scientific expedition by a practical employment in the mines. "As I have a deep conviction that such an expedition is highly important for increasing our knowledge of geology and physical science, I am exceedingly eager to devote my energies immediately to this end.
After his mother's death in 1796, Humboldt inherited the financial means to pursue independent explorations. He decided to go to Italy, where he wanted to spend a year to a year and a half researching volcanoes. From there, he wanted to travel via Paris to England, where he would board a ship to the West Indies. However, the political instability caused by Napoleon's Italian campaign in 1797 forced Humboldt to cancel his plans. In May 1798, Humboldt traveled to Paris, where he met the botanist Aimé Bonpland. After their attempt to travel to Egypt had once again failed due to Napoleon and his campaign there, the two decided to go to Madrid in December 1798.
Arrival in Spain In Madrid, Alexander von Humboldt pursued the idea of a scientific expedition to Spanish America, despite the usual restrictions on foreign travel in Spanish colonies. Through the assistance of Don Mariano Luis de Urquijo, Spain’s First Secretary of State, whom Humboldt had previously met in London, he was introduced to King Charles IV of Spain. The king granted Humboldt and his companion, Aimé Bonpland, official permission to travel throughout Spanish America for scientific purposes. The royal passports granted Humboldt and Bonpland extensive rights, including the use of scientific instruments, freedom of movement, and the authority to conduct research throughout Spanish territories.
Colonial officials were instructed to assist them as needed. Such privileges were exceptional, given that Spain had historically allowed very few foreign scientific missions in its colonies, due to longstanding policies of restricting access to outsiders for reasons of state security, economic monopoly, and religious protection. The level of trust and freedom granted to Humboldt was unprecedented for a non-Spaniard. Humboldt recognized that Spain’s primary interest in granting permission was related to his expertise in mineralogy and the potential for discovering new mineral resources, rather than purely scientific advancement.
Preparations and Objectives of the Expedition
During the months of preparation, they stocked up on literature, reviewed all natural history collections, visited experts and purchased scientific instruments which consisted of sextants and quadrants, balances and compasses, telescopes and microscopes, hygrometers and barometers, cyanometers, eudiometers, thermometers, chronometers, magnetometers, a Leyden jar and a Lunette d’ épreuve (a “proof-glass”, a deep cylindrical glass for holding liquids while under test). Humboldt and Bonpland set off from Madrid in mid-May 1799 for La Coruña in northwestern Spain, where they were to embark on the Corvette Pizzaro. Along the route, they made astronomical position determinations and altimetric measurements as normal, which might be utilized to enhance the maps of Spain.
The objectives of his expedition to America were primarily scientific in nature. Humboldt sought to systematically investigate the physical and natural features of the American continent, including its geography, climate, flora, and fauna. He aimed to carry out precise measurements of altitude, temperature, and magnetic phenomena, and to collect data on the distribution of plants and animals in relation to environmental factors. He was interested in understanding the interconnections between the earth’s physical conditions and living organisms, an approach he later described as tracing the “unity of nature.”Since he had to pay for the expedition himself, he needed sufficient capital. With the help of Jewish friends of the Humboldts, the Mendelson and Friedländer bank agreed to transfer any desired sum to Madrid without collateral or guarantees.
The Journey to South America On 5 June 1799, the Pizarro departed from the port of La Coruña after a period of delay caused by unfavorable weather. The ship, commanded by Captain Cagigal, left in the early afternoon and encountered difficulties navigating the harbor due to contrary winds, nearly running aground before eventually clearing the port. The vessel passed Castle San Antonio and the Tower of Hercules by the evening, then altered its course to avoid a British naval squadron operating offshore, a precaution necessitated by ongoing hostilities and blockades associated with the European wars of the period. Spain, originally allied with Britain and other monarchies against revolutionary France, had made peace with France in 1795. If the Pizarro had been captured at sea, the ship would likely have been taken to Portugal, a British ally, resulting in the loss of passage for the expedition’s civilian passengers to the New World.
During the voyage, Humboldt and Bonpland initiated scientific work, including the use of a dip needle to measure the Earth’s magnetic inclination and water-temperature readings, confirming previous observations by Franklin and Williams regarding ocean temperatures. The Pizarro sailed past Cape Finisterre and, on 8 June 1799, encountered an English squadron along the coast, prompting a change in course. The ship continued past Cape St. Vincent, a historic site for European maritime exploration. On 11 June 1799, the ship observed a large school of jellyfish in the Atlantic. As the Pizarro approached the Canary Islands, it passed Lanzarote on 16 June 1799, where Humboldt and Bonpland observed volcanic landscapes, including the Timanfaya volcano, which had last erupted in the 1730s. Navigation among the islands was challenging due to fog and unpredictable winds. The crew mistook a rock formation on Graciosa for a coastal castle, and the ship narrowly avoided being driven onto rocks by strong currents during the night. On 19 June 1799, the Pizarro arrived near Grand Canary. Dense fog delayed progress, but as it cleared, the ship’s company saw Pico del Teide, the volcanic peak of Tenerife, which Humboldt and Bonpland intended to ascend. British warships were observed nearby, but the Pizarro was protected by the guns of a Spanish fort and continued safely.
Tenerife Upon landing on Tenerife, Humboldt and Bonpland were received by local officials and noted the distinctive flora of the island, including bananas, papaws, and ornamental plants. On June 20, before dawn,Bonpland an Humboldt departed with guides and mules for La Orotava, near the Teide volcano. They passed through San Cristébal, built on a basalt ridge around the Peak of Tenerife, and paused to inspect rocks, eventually arriving at La Laguna, the capital of Tenerife. After the climbing Humboldt and his party left La Laguna, traversing a landscape rich in plant diversity, including palms, orange trees, vines, and cacti. The region’s natural beauty was contrasted by socio-economic inequality, with land concentrated among a few wealthy planters and the indigenous population living in poverty. The group passed through Juan de la Rambla, Victoria, and Matanza, sites of both agricultural abundance and historical conflict with Spanish conquest in the fifteenth century.
In La Orotava, they visited the botanical garden and met Monsieur LeGros, the French vice-consul, who had lived on Tenerife since being shipwrecked and agreed to guide their ascent of Pico del Teide. On 21 June 1799, the climbing party, which included LeGros, other local guides, and consular staff, departed for the volcano. The route passed solidly built but somber towns, lush gardens, and a renowned dragon tree, a species present in the Canaries but native to the West Indies, illustrating the complexities of plant distribution. The ascent led through forests of chestnut, laurels, and heaths, and onto higher, barren volcanic plains such as Llano del Retama, where vegetation diminished and only shrubs and wildlife remained. At Estancia de los Ingleses, a traditional rest point at about , the group endured a cold, windy night before continuing the climb at 3 a.m. on 22 June 1799. They crossed the Malpays, an area of broken lava and little vegetation, and reached the summit at 8 a.m.
At the peak, the party observed the structure of the volcano, measured ground temperatures, and collected air samples. The elliptical crater showed no recent eruptions inside, but the volcano remained active, with recent lava flows and geothermal activity. The summit provided panoramic views of the surrounding islands and the diverse ecological zones descending from the peak, which Humboldt recorded in a sketch. He noted five distinct vegetation zones, from grasses at the summit to cultivated tropical and temperate plants near the coast. The descent took the party back through the varying ecological regions. Humboldt made broader geological observations, considering questions about the structure and origins of volcanoes and the laws governing geological phenomena. The round trip from La Orotava to the summit and back lasted twenty-one hours. The Pizarro’s departure was delayed until 24 or 25 June 1799 due to the presence of an English squadron, allowing Humboldt and Bonpland additional time to explore the island’s surroundings. During this period, Humboldt investigated the fate of the Guanches, the indigenous people of the Canaries, concluding that they had been destroyed by European conquest and slavery, with survivors assimilated into the Spanish population.
The Pizarro crossed the Tropic of Cancer on June 27, sailing through the Atlantic and carefully avoiding the area labeled “Bank of Maal-strom,” whose dangers Humboldt doubted existed in the calm tropics. The ship passed west of the Cape Verde Islands, once claimed for Portugal by Alvise da Mosto, and entered the Sargasso Sea, a vast region of floating seaweed previously described by Columbus. Here, the crew encountered a partially submerged, abandoned ship covered in seaweed, which Humboldt surmised had drifted from the rough North Atlantic rather than sinking locally. Throughout the voyage, Humboldt and Bonpland conducted systematic scientific observations, measuring a wide array of atmospheric and oceanic variables and recording them meticulously. The two naturalists spent their evenings observing unfamiliar southern constellations, including the Southern Cross, which stirred Humboldt’s sense of distance from Europe.