Here are the most recent Nielsen ratings of TV viewership of people age 12 and up for the TV markets that serve Iowa as well as each markets ranking. 

Nielsen Markets

Cedar Rapids/Waterloo/Iowa City/Dubuque (87)

Des Moines/Ames (75)

Mason City, IA/Rochester/Austin, MN (154)

Omaha/Council Bluffs (69)

Quad Cities (98)

Sioux City (149)

*Last Nielsen TV Market Rating effective 09/30/2018.