Illinois - Green River
Originally the product of a brewery facing restrictive Prohibition policies, Green River grew to be Illinois' favorite soft drink, and has been produced by a multitude of bottlers over the years.
Indiana - Triple XXX
Although it was founded in Texas, Triple XXX is now an Indiana institution that's famous for its root beer, and for the fact that only one of two remaining eponymous restaurants is located there.
Iowa - Sioux City Sarsaparilla
Named after the Iowa city, Sioux City Sarsaparilla is widely regarded as one of the best sarsaparillas out there and was even mentioned in The Big Lebowski. Damn, dude.
Kansas - Lost Trail Root Beer
A tried-and-true Kansan brew, Lost Trail's root beer has been made in-state since the frontier days.
Kentucky - Ale-8-One
Around its production center in Winchester, Kentucky, Ale-8-One is a supremely popular ginger-and-citrus soda. It's also the only soda invented in Kentucky to still be in existence. So there's that, too.
Louisiana - Delaware Punch
Despite its name, this drink isn't affiliated with Delaware (it's actually named after a grape variety), rather it's a Southern fruit soda with a grape kick that's found in select stores in the Louisiana area.
Maine - Moxie
Even though it was originally invented and produced in Massachusetts, no state is more nuts for the weird flavor of Moxie than Maine, which has even gone so far as to name it the official state soft drink.