This is the government for you:
Definition of Rural: The Census Bureau defines rural as any population, housing, or territory NOT in an urban area.
https://storymaps.geo.census.gov/arcgis ... cb65ad942a
"To account for the increase in suburbanization, the 1950 Census defined urban by identifying densely settled urbanized areas with populations of 50,000 or more. Incorporated places and census designated places with populations of at least 2,500 and less than 50,000 located outside of urbanized areas were also included as urban. This definition was used until 2000.
Urban clusters were first introduced in 2000 to replace urban places outside of urbanized areas.
The Census Bureau delineated 3,573 urban areas after the 2010 Census for the United States:
486 Urbanized Areas
3,087 Urban Clusters"
I took a look at my home state. A lot of smaller cities surrounded by rural areas are classified as urban. I'm sure those places helped to offset the "fully urban" areas like Detroit, Chicago, and other crapholes.