Mojave Desert is in San Bernardino County.
The majority of visitors to the Mojave Desert see it only through their car windows as they traverse I-15 to Las Vegas. But the beauty and isolation of this desert is immense and should be experienced first-hand by travellers with time and adequate vehicles and supplies.
The Mojave Desert is located between Los Angeles and Las Vegas on Interstate 15. Highway 395 passes through the middle from Victorville in the south; Highway 14 comes in from Lancaster in the southwest. Highway 40 runs from Barstow, roughly in the middle, out through Needles in the east.
Scarce airports are in the area; most have really long runways and rainy, stormy weather; few have commercial flights.
Aside from main roads, most of the Mojave is criss-crossed with dirt roads; some of these are shown as standard roads on maps; others are unmarked. In either case you should have a medium- to high-clearance vehicle, with four wheel drive if you plan extreme backcountry driving.
The best way to experience the Mojave is to camp. Much of the area is BLM land, with open camping allowed.
When travelling in the desert, follow the standard precautions; carry any needed parts and fluids for your vehicle, and at least a gallon of water per day for drinking. Rattlesnakes will only bite you if they feel threatened.
To the North of the Mojave desert is Death Valley.