No, the Mammoth Gravel Classic is not May 2nd. The travelwisconsin.com page has bad info. That is the Woolly Bike Race on the Woolly single track trails.

Joining the Woolly Bike Club

The Woolly Bike Club is an IMBA Chapter.  To become a member of the club, join IMBA at an Individual level or higher and designate Woolly as your chapter.

Part of your membership fee goes directly to the Woolly while the rest goes to IMBA to support national mountain bike advocacy.

To join head over to the IMBA website.

Woolly IMBA Logos