The story
The cities in Vermont and Kentucky were named after Montpellier, France, despite the spelling difference in the modern spellings; and it is likely that many others were also named after that French city. The city in Iowa was named after the city in Vermont, and it is likely that at least some others were also named in that fashion (i.e., one U.S. city after another U.S. city).
Etymology from Wiktionary, CC BY-SA 4.0.