The date is 18 April 2021 and the event is the Salton Sea 400, an endurance motor scooter event that circumnavigates southern California’s Salton Sea. The Motor Scooter International Land Speed Federation is the group that put the event together (they do this sort of thing regularly), and I can tell you from personal experience that Alan Spears and the MSILSF crew are a good bunch of people. I rode a 150cc California Scooter (along with good buddies TK and Arlene) in a similar event around Death Valley a few years ago and it was a hoot.
The contact info is in the poster above and here (and you should register to run in the event). If you have a scooter and you’d like to run it around the Salton Sea, you might consider participating.