Friedrich Wilhelm Heinrich Alexander von Humboldt was referred to by Charles Darwin as "the greatest scientific traveler who ever lived." Born in Germany and trained as a geologist at the Freiberg Academy of Mines, his exploration began at the age of 27 when his mother died and he inherited a substantial estate. He obtained approval from the King of Spain to explore South America, and for 5 years traveled extensively in the Spanish territories, covering 6000 miles on foot, horse and canoe. Upon his return, he spent 23 years in France and enjoyed life among the greatest intellectuals of the time, until his finances ran out and he returned to be an advisor to the King of Prussia where he earned a steady income.
Along with Thomas Jefferson, von Humboldt was considered one of the last universal scholars, as scientific knowledge became too vast for any individual to master.
He wrote extensively about his travels and at the age of 79 began publishing Kosmos, summarizing all that was known about the earth at that time. He was working on the 5th edition at the time of his death.
Von Humboldt's specific contributions to geography include the creation of the Isotherm and Isobar, lines on a map connecting locations with the same temperature and barometric pressure, respectively.
See AttachmentBy studying Andean volcanos he also disproved theories of how the earth's crust was formed. His studies of South American culture also included descriptions of political, social and economic descriptions, inextricably connecting the study of places with the demographics that define them.
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Famously, he was quoted as saying 'the most dangerous worldviews are the worldviews of those who have not viewed the world," which seems highly relevant today.
Resources:
Maps of his travels in South America: http://library.sc.edu/digital/collections/humboldt.html
Biography: https://www.britannica.com/biography/Alexander-von-Humboldt
Quotes: https://www.goodreads.com/author/quotes/303739.Alexander_von_Humbolt