Pitou, you are quite correct. Napoleon sold the Louisiana Territory (essentially, all lands drained by the Mississippi River) to the fledgling United States in 1803 for about 3,000,000 dollars. I don't want to think about what that amount would be if adjusted for inflation over 200 years. Anyway, Napoleon needed the money to finance a war. He wasn't interested in such a distant territory. We needed the land to support westward migration of our people. Though the truth is, we didn't really want that much. But Thomas Jefferson knew a bargain when he saw it. A mutually acceptable deal was struck and the Lousiana Territory became the property of the United States. Louisiana became a state in 1812, was part of the Confederacy during the American Civil War (also known locally as the War of Northern Aggression, and that will SURELY get a rise out of someone...)
The Cajun territory is actually the home of folks who left Arcadia, Nova Scotia, Canada after the UK took over Canada from France. As told by the late Justin Wilson, a Cajun humorist, the Arcadian people wouldn't swear allegiance TO the King of England, they would only swear AT him. So they sailed south around the tip of the Florida peninsula and nestled in the marsh country to the southwest of the current location of New Orleans.
That area has undergone a metamorphosis of cultures, becoming a true melting pot of the people who have settled there, including Spanish, French, English, Dutch, German, and Native American (Choctaw tribe) cultures. The name "Cajun" is itself the result of a linguistic drift resulting from different accents pronouncing "Arcadian" incorrectly. It went to "Arcadjian" and then to "Cadjian" and then to "Cajun" over a couple of hundred years.
Some other linguistic differences:
In English, "I do not know" becomes French "Je ne c'est pas" but Cajun "Pas ca ne"
In English, "Potato" becomes French "Pomme de Terre" but Cajun "Potat" (both T's pronounced hard and elision does not occur for T in Cajun like it would in French.)
My wife is Cajun, from the area of Thibadaux, LA. If you can't find it on any maps, look for Houma, LA or Lafayette, LA. It is close to there. Her REAL home is Chac Bay, but don't bother to look for that on a map. You won't find it unless you are a real map freak.
By the way, if you DO happen to look at a map of south Louisiana and some of the names look French but don't make sense, it is because they are French spellings of Choctaw words. Because, of course, most Native American languanges weren't written until the French got here. As a result, we get street names like Tchopitoulas (the French spelling of the name of an old Choctaw tribal chief.)
See what you get when you make a side comment in a post?