The cities Kahoka, Keokuk and Nauvoo are all close by in what American tri-state region?

All three cities in question - Keokuk, Iowa (in uploaded photo); Nauvoo, Illinois; & Kahoka, Missouri - are either on or close to the Mississippi River. Keokuk is in fact on the confluence of the Mississippi & Des Moines Rivers; a small southeast-most piece of the latter forms a limited natural boundary between IA & MO. The eccentric billionaire Howard Hughes spent his childhood in Keokuk with his uncle Rupert nearby.

The Illinois-Iowa-Missouri (IL-IA-MO) tri-state region is officially called the Fort Madison-Keokuk micropolitan area; the two said cities are dual seats of Lee County, IA, the southeast-most county & only one of the state's 99 counties with two seats. Directly south thereof is Clark County, MO, named for William Clark, half of legendary explorer tandem Lewis & Clark.

Long before making the whole state of Utah - & particularly Salt Lake City - synonymous with their faith, the Mormons acquired land in IL cross-river from MO late in 1839 and named it 'Nauvoo' (Hebrew for 'they are beautiful') and established their first temple there.

Keokuk and Kahoka may sound similar but have different meanings. Keokuk is named for a chief of the Sauk tribe, mostly indigenous to the future area of Green Bay, Wisconsin. Kahoka is a corruption of Cahokia, a subset tribe of the Illinois or Illiniwek Confederacy; incidentally, Cahokia IL is just across the Mississippi from MO, roughly equidistant from the IL-IA-MO tri-state area & St. Louis.