The Monadnock Region is a region in southwestern New Hampshire. It is named after Mount Monadnock, a 3,165 foot isolated mountain, which is the dominant geographic landmark in the region. Although it has no specific borders, the Monadnock Region is generally thought of comprising all of Cheshire County and the western portion of Hillsborough County. The largest municipality, and only city, in the region is Keene with 23,409 residents.