Alabama is home to many privately-owned ATV parks where you can develop and challenge your riding skills. But there are also plenty of natural areas that are ATV-friendly, like the Kentuck ORV Area in the Talladega National Forest, which has miles of trail system that negotiates a mixed hardwood forest. A newer ATV trail was recently developed in Buck's Pocket State Park in the northern part of the state. One thing to keep in mind when riding in Alabama is that ATVs are not allowed on Gulf Coast beaches or sand dunes, unless they're privately owned and you have the owner's permission.
Check out these Knoxville, AL ATV/OHV resources:
