The Iowa State Data Center is a great place to search for Iowa-focused data on: employment/unemployment, health, housing, income, language, population, poverty, race.
Iowa data is reported at the state, county, or in some cases metropolitan area/city/town level.
State-by-state comparisons are available for many variable.
Data ranges often cover ten to fifteen year spans (e.g. from 2005 to 2016).
County Quick Facts provide population data from 1850 to 2017 as well as current data on age, characteristics of commute to work, disabilities, educational attainment, ethnicity/ancestry, gender, household size, income, occupation (by general category), poverty rates, race, unemployment rates, and veteran status for each county in Iowa.
City Quick Facts (same as above - but for hundreds of Iowa towns and cities).