Arnolds Park is a city in Dickinson County, Iowa, United States. The population was 1,110 in the 2020 census, a decline from the 1,162 p…Arnolds Park is a city in Dickinson County, Iowa, United States. The population was 1,110 in the 2020 census, a decline from the 1,162 population in the 2000 census. According to the United States Census Bureau, the city has a total area of 1.57 square miles, all land.