A large dust 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.

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. Most notably, it’s the birthplace of the Ultra4 series, which includes the Race of Kings—commonly called the world's toughest single-day off-road race—which combines 100-mph-plus desert racing with highly technical rock crawling.

At 245 miles, this year's race was the most difficult to date. Only two teams finished under the 14-hour time allotment. The event now draws over 80,000 attendees, who can purchase general admission tickets starting at £100, and features approximately 750 racers, both professional and amateur, from all over the world. People can watch at home too: organizers say that 1.2 million viewers watched online this year.

As King of the Hammers enters its third decade, it's clear how far off-roading has come from the days of “shit-box” trucks covered in dents and stickers to logo-emblazoned purpose-built rigs easily costing into the hundreds of thousands. Ultra4 races occur internationally, and the off-road vehicle market is valued at more than £14 billion, according to Grand View Research.