The Historic Roadside Marker program is administered by the state of New Hampshire’s Division of Historic Resources. Their website can be found HERE.
Details of the Historic Marker program requirements can be found HERE.
You can view all of the currently installed Historic Markers HERE.
Additional information about paintball’s history can be found on WIKIPEDIA (which is slightly out of date and partially incorrect), on the Paintball X3 History site (more accurate and detailed), various other websites and in books including The Survival Game Manual, The Complete Guide to Paintball and A Parent’s Guide to Paintball.
Bob Gurnsey’s website (game founder) can be found HERE.