Iowa enforces anti-stacking clauses and aims at the highest single limit
Iowa's rules are in Iowa Code 516A.1 (required coverage and rejection) and 516A.2 (construction, minimum coverage and stacking). The minimum limits are in 321A.1, and the injury deadline in 614.1.
Read how stacked and single-limit coverage differ in Iowa, check what section 516A.2 says, or see how UM and UIM work in Iowa.