Before the Seven Years War (1754/1756-1763), large portions of the North American continent were French territory. In fact in sheer geographic terms, the French Colonies in North America were considerably larger than the English (though also considerably less populous).

While most of France's colonial efforts in North America were focused on Acadia, the Saint Lawrence River Valley and the Caribbean, France also controlled a vast territory roughly corresponding to the middle third of the Continental United States which they called "La Louisiane" (Louisiana). France's interest in this territory was primarily the trade in Beaver Furs as well as keeping it out of the hands of the British and the Spanish and as a result only a relatively small effort was made to attract French Settlers.

In order to facilitate trade with the natives as well as exert some semblance of control over the vast Louisiana colony, French officials based out of Québec City and Montreal made efforts to explore the interior and construct trade forts in strategic locations. Because the French had explored the territory and constructed its earliest settlements the names of many parts of the midwest have their origin in the French Language (though the pronunciation has been highly Anglicised since the end of french rule).

The French explorers/traders/soldiers understood where the best locations to build a settlement were and as a result many of the forts they constructed in the 17th and 18th centuries formed the nucleus of what would become much larger American Cities.

To answer your specific question regarding the "ville" part of Louisville, "ville" is a French word that means "city." Louisville therefore in French means the city of Louis, or Louis' city. "Louis" is likely a reference to French King Louis XIV, France's King at the time that René Robert Cavelier Sieur de la Salle explored the Louisiana territory and the man for whom Louisiana is named. You'll find other parts of the United States with French Heritage which has largely been forgotten by most Americans but is preserved in the names of places such as: St. Louis named for French King Louis IX, Detroit taken from the French word for a strait, Mobile (originally Fort Louis de la Mobile), Baton Rouge (from the French Bâton Rouge meaning Red Stick) and New Orleans named for the city of Orléans near Paris.

Other toponyms are less obviously French in origin due to having been translated into English. Examples of this include Grand Forks (Grandes Fourches), Little Rock (La Petite Roche) and Green Bay (La Baie Verte). Others like Des Moines and Boise have kept their French Spelling but lost the pronunciation. "Arkansas" and "Illinois" are not spelled as they are pronounced because the names are French approximations of native words as well.

There's a lot more I could say about the French Colonial Presence in North America, which as evidenced by the continuing presence of the French Language in my home Country (Canada) and to a lesser extent in the United States, left a fairly great though largely forgotten legacy. If you have any questions about French North America or would like some book recommendations, I'd be more than happy to oblige.

Just as a bonus little piece of information: The Cadillac Car Company is named after the founder of Detroit Antoine de la Mothe Cadillac who for a time lived in Montreal on the site of what is now this McDonald's.