Answer: The tsunami occurred on 1958 at Lituya Bay, Alaska.
The Lituya Bay tsunami occurred on July 9th, 1958, northeast of the Gulf of Alaska. It was as a consequence of a strong earthquake of magnitude 8.3 on the Ritchter scale along the Fairweather Fault in the Alaskan Panhandle, which caused a landslide in a fjord in Lituya Bay, collapsing an entire mountain and generating a gigantic wave that rose to 524 meters, the highest recorded so far.
It should be noted that despite its great magnitude and having uprooted all the trees and vegetation of the place, this mega-tsunami claimed only five lives because the area was not as inhabited as the large cities are.