Is it pretty much the same story for Mackinac/Mackinaw?
Link to the article:
The truth us that we pronounce it that way to confuse Yankees.
Not quite. In the case of Mackinac Island, the original name used by the local Indians was mishimikinaak. That was transcribed by the French as Michilimackinac. It means “Big Turtle”, apparently (probably a description of the look of the island in the water).
It should be noted that another localish tribe (the Menominee) had the similar word maehkaenaw for turtle. It’s possible that the French trappers eventually substituted this pronunciation for the -ak of the original. By the time of the settlement of Mackinaw City, the pronunciation was clearly accepted as being -aw, since the city decided to spell it that way for clarity.
And it doesn’t confuse people from Kansas in the least, since they pronounce the river, and the state, arkans-ass. 
I saw an NBC pronunciation dictionary for announcers from the 1960s, they were pronouncing the state “ARKansaw” and the river arKANsas.
Combining that and previous post, my understanding is that the river and town (Arkansas City) are called arKANsas in Kansas (and perhaps the river is called that in Colorado too where it rises and Oklahoma downstream). People in Arkansas though call the river as well as their state ARKansaw, which is also more common nationally for the river, and people in KS or CO don’t necessarily call the state ArKANsas.
I would say the name of the state is ARKansaw, either name could be used for the river but ARKansaw is preferred for people who don’t come from the area near the river upstream of the state, and the town in KS is definitely ArKANsas City.