 In 1938 a part of Norderhov with 268 inhabitants was moved to Hønefoss, and on 1 January 1964 the rest was merged with Hønefoss, Ådal, Tyristrand and Hole to form the new municipality Ringerike.Norderhov was by far the largest municipality prior to the merger, with a population of 15,143.The municipality (originally the parish) was named after the old farm Norderhov (Old Norse