Orange City is a city in and the county seat of Sioux County, Iowa, United States. The population was 5,582 at the 2000 census. Named after William of Orange, it is best known for its Dutch background, which it celebrates by having an annual Tulip Festival for 3 days of every May and facing many of the city's buildings with Dutch architectural fronts. Orange City is home of the headquarters of Diamond Vogel Paints.