Maine was the most rural state according to the 2010 census.
Census: Maine most rural state in 2010 as urban centers grow nationwide
"According to the new data, 61.3 percent of Maine’s population lived in rural areas. “Rural areas” are all those that aren’t classified as “urban.” The Census Bureau views areas with populations of at least 2,500 as urban — though it differentiates between urban clusters (at least 2,500 people and less than 50,000) and urbanized areas (50,000 or more people)."
Population: 1,328,361
The 3 Urbanized Areas:
Portland, ME Maine 203,914
Includes all or part of Portland, South Portland, Scarborough, Old Orchard Beach, Saco, Gorham, Westbrook, Falmouth, Yarmouth.
I don't think anybody except annoying large city people would consider the Portland area rural.
Bangor, ME Maine 61,210
Includes all or part of Bangor, Brewer, Orono, Old Town, Milford
Lewiston, ME Maine 59,397
Inculdes all or part of Lewiston, Auburn, Sabattus
24 Urban Clusters
Lots of small towns. Administratively challenging.
Because there's so many small towns, there are other pockets where there's a busy 15-20k magnet for smaller towns around it.