It’s all in the vowels. So says linguist Corrine McCarthy from George Mason University. She recently spoke to WBEZ’s Curious City about the Chicago accent. But those vocalic peculiarities, as exhibited to comedic effect by an SNL sketch about Bears super fans, are only just the tip of the linguistic iceberg.
You can read (or listen to) the entire post to learn more about what other dialects are home to Chicago.
To answer the initial question, though, of where our unique accent comes from, UIC’s own Richard Cameron is quoted as saying that a likely possibility is that “the first dialect that gets [to a place] seems to win.” In our case then, it seems that that would be New Englanders in the mid-1800s.