Desolation Trail is a primary access to the Wasatch Mountains. The trail starts at the South Box Elder Picnic area just East of The Mill Creek Inn restaurant.
The trail was originally designed as a motorcycle route. As such, it takes several switch backs with a consistent grade.
The trail South side of the canyon and has a North Facing Slope. In Utah, North facing slopes tend to be more sheltered and cooler. The trail goes through old growth pine forests.
If you wish to take a steeper hike. Thaynes Canyon trail parallels Desolation. It is much steeper and goes straight up this short side canyon. Most people take the Desolation trail as it has more view areas.
After gaining elevation the Desolation Trail connects with other trails in the Wasatch Mountains including Neffs Canyon Trail, Porter Fork Trail, Mill B (which drops into Big Cottonwood Canyon). The travels through the Mount Olympus Wilderness Area, winds to the South of Mount Raymond and eventually leads past Dog Lake to Desolation Lake (most people who want to visit Desolation Lake drive to the top of Mill Creek Canyon and take the Big Water trail.
Although the trail was built for motorcycles, it has eroded to the point that it is not a good bike trail. For that matter, since it goes through wilderness, bikes probably aren't allowed on the trail.