cloud hovers over the otherwise clear Johnson Valley in Southern California. Just past the town of Lucerne Valley, a plot of public land is filled with all manner of off-road vehicles: dirt bikes, first-gen Toyota trucks with welded roll cages, brand-new Broncos, tiny four-wheelers piloted by children, and UTVs. RV campsites sprawl into the desert on either side, a temporary structure houses a bar and restaurant, and the road ends at a vendor village that could rival a small county fair. Welcome to Hammertown, the temporary desert city that springs up every January for 16 days for an off-road race series known as King of the Hammers. Think Burning Man meets Mad Max, but sponsored by Monster Energy. Having recently completed its 20th year, Hammers started as a contest between 13 friends and now comprises a series of races featuring everything from dirt bikes to VW Bugs to million-dollar trophy trucks.…