North of Portsmouth and northwest of York, the Mount Agamenticus area has a 25 mile horseback riding trail system.
To reach the horseback riding trailhead from the south including Portsmouth, head north on US95 to Exit #7. Head across the bridge to the west side of the highway. Turn right heading north on Chases Pond Road for 3.5 miles. Turn left heading west on Mountain Road for 2.7 miles. At this point, you should reach an intersection with the Mount Agamenticus access road. There are several trailheads with the first located here on the right (north) side of the road.
Overall, Mount Agamenticus is the 3rd most popular horse trail of all 3 horseback rides in Maine.