Herron Island is an island in central Case Inlet in the southern part of Puget Sound in the U.S. state of Washington. The Pierce County island has a land area of 1.2326 km² (304.57 acres) and a population of 151 persons as of the 2010 census. Herron Island is one of the few privately owned islands in Puget Sound. All access to the island is by boat, mostly aboard the HMC ferry, the "Charlie Wells", and a guest pass signed by an HMC member is necessary to board the ferry. The island is 1.25 miles (2.01 km) long, and 1/2 mile (800 m) across.