Lake Tahoe was discovered by John Fremont in 1855 -
Fremont was a United States Army officer, explorer, and politician who
became a California Senator in 1850. The Lake Tahoe region of the Sierra
Nevada mountain range and the Great Basin of Nevada was discovered and
charted by Fremont and his team during his second of five expeditions
into the American west.
The term 'discovered' is relative to the observer and the history teller -
prior to John Fremont, Lake Tahoe had been inhabited by Native Americans for
~10,000 years. The Lake Tahoe and surrounding Sierra Nevada mountain region
was inhabited by the Martis people and later by the Maidu and Washoe people.
The Tahoe-Truckee, Donner Summit, and surrounding Sierra Nevadas was a perennial summer
destination for nearby tribes - accessing the Lake's resources and natural bounty was a must. The Sierra region became a meeting
grounds between neighboring tribes - Native Americans each side of the slope
would meet and encounter tribes from the west (California) side.
https://taylortallac.org/tahoe-and-its-people/
https://en.wikipedia.org/wiki/John_C._Fr%C3%A9mont
https://www.truckeehistory.org/native-americans.html