Elevation dictates what octane levels are available. Higher altitudes require less octane because of lower atmospheric pressure reduces maximum cylinder pressure.
Since most of KS is well within Clean Air Act pollutant levels, the need for oxygenates is minimal and this allows better freedom in the marketing. The central location means many different refineries can sell their products there and because of the surrounding regional requirements, many different blends can be had, it just depends on price and availability.
In reality, only two grades come from the refinery though the pipelines, 87 and 91 octane. At the terminal where the tankers are filled, gasoline is blended to the desired octane and many times, additional components are added to boost detergent, octane or oxygenates.
That is how you get octanes over 91 and in between. 89 octane is a 50/50 blend of 87 and 91. 93 is 91 pipeline grade with octane boost, usually MTBE.