Udell is a city in Appanoose County, Iowa, United States. The population was 28 at the time of the 2020 census. Udell was founded in 1895. It …Udell is a city in Appanoose County, Iowa, United States. The population was 28 at the time of the 2020 census. Udell was founded in 1895. It was named for Dr. Nathan Udell, a pioneer settler. According to the United States Census Bureau, the city has a total area of 0.32 square miles, all land.