The term 'Long Island Sound City' refers to two cities located on the Long Island Sound in the Northeastern United States. The first city is RYE, a city in Westchester County, New York with a population of about 15, 000 people. It is known for its historic downtown area and its waterfront parks. The second city is Darien, a town in Fairfield County, Connecticut with a population of about 21, 000 people. It is known for its beaches, marinas, and golf courses.