While Billerica State Forest is a relatively small 370 acres DCR property divided by roads into three parcels, it has fast become a local gem for mountain biking, trail running and hiking.
Since there are currently no designated parking lots, most riders access BSF from Russell Mill Town Forest in Chelmsford. However, there is limited parking on the side of Rangeway Road, next to Rte 3.
The Gilson Hill side of BSF contains the majority of the high quality and exceptionally fun singletrack trails. Riders usually begin by ascending Yellow Rabbit and then navigating around the Gilson Hill Loop. The top of Gilson Hill is the second highest point in the Town of Billerica. After finishing the Gilson Hill Loop, one can ride the Northern Loop either clockwise or counter-clockwise, however riding the loop clockwise maximizes the downhill/enduro features of the trail. There is also a very fun lollipop trail called The Inner Loop off of the Northern Loop.
On the northern side of Rangeway Road is a small but fun <3-mile loop, and if one wishes to put in an extra mile, you can cross Chelmsford Road and do a short loop around the Manning State Forest. However, be aware that this section is intensively used by walkers and people using the exercise stations along the path.
The attached GPX file is a 18-mile ride that includes most of Russell Mill and the Billerica State Forest trails. For a shorter ride, you can beeline it to Billerica.
Merrimack Valley NEMBA is responsible for most all of the best trails in both Russell Mill and the Billerica State Forest, so be sure to support them by joining their chapter. Read more about Billerica State Forest