Motorcycle rallies (biker rallies) are simply gatherings of riders and motorcycles at specified times and places usually with attendant vendors, food, games, and other activities.
Motorcycle rallies or biker rallies may last from a day to more than a week. Some major motorcycle or biker rallies are built around organized professional motorcycle races.
Motorcycle rally attendance varied widely from a low of a couple of dozen riders or less to huge organized rallies with hundreds of thousands of riders.
My updated article, Motorcycle Rallies (Biker Rallies) - Major Rallies for Motorcycles, gives basic information about motorcycle rallies. The second page of this article contains my list of the top motorcycle rallies.
The picture shows me raising my arm after I parked my bike on Main Street at the 1993 Sturgis Rally. That was the year of the great Midwest floods.