Dauphin is a borough in Dauphin County, Pennsylvania, United States. The population was 791 at the 2010 census. Dauphin's ZIP code is 17018. It is part of the HarrisburgCarlisleMetropolitan Statistical Area. Dauphin is located at 402200N765552W / 40.366687N 76.931168W / 40.366687; -76.931168. The land at Susquehanna River's edge is alluvialflood plain, but Dauphin sits at the head of a narrow valley between two mountains, at the mouth of Stony Creek. The valley between the two mountains is called Stony Valley, which contains the villages of Singersville and Ellendale Forge. This section along the Susquehanna River is a gateway from the southeastern plains into the Appalachians and the north-central part of the state. Dauphin is surrounded by Middle Paxton Township, which itself comprises mountains and valleys south of the confluence of the Susquehanna and Juniata rivers to the west. From south to north, the mountains are named: Blue Mountain, Second Mountain, Third or Stony Mountain, and Peters Mountain. The eastern end of these valleys are generally undeveloped state game lands and protected watershed.