Crossword puzzle clue "chair of state"

Uses, as a chair - or the floor if you don't understand what a chair is

Illinois, Indiana, Iowa, Michigan, Michigan State, Minnesota, Northwestern, Ohio State, Penn State, Purdue and Wisconsin

Chair of state

Article of tropical apparel ... whose start is a state nickname for the state indicated by the circled squares

Unlikely state of a state?

Secretariat's mother, for one ... whose start is a state nickname for the state indicated by the circled squares

State made up of two state postal abbreviations

Emergency worker ... whose start is a state nickname for the state indicated by the circled squares