How many counties are there in Iowa?

99.

Iowa has 99 counties. According to the 2009 County Population Estimates, published by the US Census Bureau, the top 3 populated counties are: Polk (429,439), Linn (209,226) and Scott (166,650); Adams is the least populated county, with only 3,930 residents. The county with the greatest population decrease is Cerro Gordo, with minus 2,838 residents from 2000 to 2009.