The triangular shaped island became a peninsula in the early 20th century when the Gallaudet Aircraft Company constructed America's first seaplane-only factory at Chepiwanoxet in 1916. To allow truck access to the factory, the south channel to Greenwich Cove filled in with sandy gravel dumped into the marsh, making a causeway from Alger Avenue that still remains. As a result of blocking water circulation around the island, Arnold Cove lost its small boat access from silt deposits in the tidal marsh located on the North side of the island. With the island made of glacial outwash sand deposits it remains subject to shore erosion. The Gallaudet Company built wood bulkheads around the North, East and South shores with rock rip-rap on the waterside and fill behind. With many factory workers living north of the old cove, a narrow wood plank bridge was built across the marsh to allow quicker access to/from work.