Diagonal is a city in northwest Ringgold County, Iowa, the United States. The population was 344 at the time of the 2020 census.
The community was named for the fact that two railroads intersected diagonally near the town site.
Geography
Diagonal is located 5 miles west of US Route 169 and approximately eight miles northwest of Mount Ayr. The Grand River flows past the east side of the town.
According to the United States Census Bureau, the city has a total area of , all land.