West of Concord in Merrimack County, there is an extensive trail system around Henniker Trails. In the past, these trails were maintained by the Contoocook Valley ATV Club, which disbanded prior to summer 2005. Many of these trails and bridge network are maintained by the Henniker Trail Travelers club and the Army Corps of Engineers. Portions of the trail system are closing due to bridge loss and change in private property. Be very careful to ride only on approved routes (which can be difficult to determine). You really need to contact the Henniker Trail Travelers club to find out the latest status of OHRV usage on these trails.
Note: The State Of New Hampshire requires a NH state registration tag on every ATV. An out-of-state registration tag is not valid in NH. They will issue a fine if you try riding without a NH tag.