On May 28, 1807, Swiss paleontologist, glaciologist, and geologist Jean Louis Rodolphe Agassiz was born, who is considered a prominent innovator in the study of the Earth's natural history. He was the first to scientifically propose that the Earth had been subject to a past ice age.
On May 14, 1804, American explorers Meriwether Lewis and William Clark departed for the first American expedition to cross what is now the western portion of the United States, departing from St. Louis on the Mississippi River making their way westward through the continental divide to the Pacific coast.