The cache is not at the posted coordinates. The posted coordinates will bring you to a sign explaining who Kancamagus was. To find the cache, answer the following questions.
Final Coordinates: N 43 59.4AB, W 71 10.7CD
AB = The last 2 numbers year Kancamagus became the Sagamon of the Penacook Confederacy minus 49
CD = The last 2 numbers of the year Kancamagus fled to northern New Hampshire or Canada minus 55