The Horn Canyon Trail begins just before you enter Thacher School, be sure to follow the 'HC' signs that point you to where the single track begins. Once on the trail, you cross the creek a few times before a steep climb up to The Pines Camp (2.7miles) and ultimately Nordhoff Ridge Rd.
The Pines Camp has three campsites set underneath Coulter pine trees that were planted after the 1948 fires. A few of the trees were lost during the Wheeler Fire of 1985 and most of the others were starved out during the drought of 2012-2016. Water is sometimes available at a spring behind the camp. Note that The Pines Camp was closed in 2015 due to hazard trees.
Horn Canyon Trail is most commonly used as a dayhike route but can be part of a larger trip into the Sespe or looped in as part of a long mountain bike ride with other nearby trails.