Conversation so far:
what was snake river canyon in regards to evel knievel ?
The launch took place at the south rim of the Snake River Canyon.
what was the launch of?
Knievel hired subcontractor and aeronautical engineer Doug Malewicki to build him a rocket-powered cycle to jump across the Snake River.

Question: when was the launch?
Self-contained rewrite: when was the Evel Knievel at snake river launch?