Joshua Tree National Park was my first backpacking trip. My husband and I did an out-and-back, overnight trek along the Boy Scout Trail in the Mojave Desert section of the park, about 12 miles total. Before this, I'd never explored a proper desert on foot, and I was amazed by the variety of vegetation, from rotund red cacti to the titular, crooked joshua trees.
The first part of the trail (coming from inside the park) shoots through a wide open landscape with large rock formations; in the second, more plants crop up, creeping closer to the trail; the final leg winds through a rocky canyon. That variety makes it a great trail for first-time backpackers, especially in the winter when the temperature tops off in the low- to mid-seventies.