Why isn’t the last two syllables of Arkansas pronounced the same as Kansas?
This site mentions that the pronunciation is a result of resolution by the Arkansas Legislature in 1881. The reason given is that it follows the pronunciation that the French settlers got from the native Americans for the area.
That’s what cut-and-psste does. I had a website but the address failed and now I can’t find the site any more. This is the address which worked once but not fails. ahttp://tafkac.org/books/legman/arkansas_pronunciation.html
But that 1881 law only made official the way that most Arkansawyers already pronounced their state. (BTW, remove the first letter of that url to get it to work.)
Both names were first recorded by the Jolliet/Marquette expedition of 1673 down the Mississippi, along with 8 other state names plus Chicago. Kansa was the name of a tribe they heard about that lived up the Missouri. Akansea was a large village where a river (now known as the Arkansas) flows into the Mississippi and the expedition decided to turn back. The latter somehow got modified to Arkansa and both names were pluralized to come up with the current spellings.
So it’s a bit of a coincidence that the names are spelled so similarly. They’re pronounced different because they’ve always been pronounced differently.
But just because something is spelled Arkansas, don’t assume it’s pronounced AR-kun-saw. There’s the ar-Kan-sas River, and ar-Kan-sas City.
I didn’t know there are pirates in Kansas. 
Uh, I’m pretty sure it’s the AR-kun-saw River everywhere outside of Kansas. Arkansas City is also in Kansas. For some reason, Kansans just can’t grasp the idea that something ending -kansas could be pronounced differently than Kansas is. :dubious:
And that’s why everyone just says Ark City.
I’ve heard plenty of Missouri and Arkansas residents pronounce the Arkansas River as “ar-Kan-sas” too.