Vermont and New Hampshire aren't the largest states in the country, however they do have some big 4-wheel riding opportunities.
Vermont offers up its Green Mountain National Forest for your 4-wheeler riding pleasure. There are several trails in this 821,000 acre space. The trails are well maintained and offer challenges for 4-wheeler riders of every skill level. Most of the trails are easy to moderate in navigation skill required to use the 4-wheeler trails, with the exception of the Ash Hill Trail which is very difficult and even experienced 4-wheeler riders will find it is a very challenging ride.
New Hampshire with it's dense forests, offers a great amount of riding fun for you on your 4-wheeler. White Mountain National Forest offers the most bang for your buck with over 800,000 acres of land to explore. The trails are clearly marked and the usual Forestry Service rules for riding your 4-wheeler apply; such as you must have a spark arrestor and noise muffler in place on your 4-wheeler prior to riding.
You will be sharing the 4-wheeler trails with bikers, hikers, and other 4-wheeler riders and these are heavily traveled 4-wheeler trails. The Treadlightly standards are heavily in place, and the "Leave No Trace" program is very much in place here and even though there is a lot of 4-wheeler activity and other traffic, the trails are very well maintained.
As you can see both the small states of New Hampshire and Vermont offer some big riding for you and your 4-wheeler.