Detroit

Detroit is first mentioned by Future!Dean in 2014.^{5.04 The End} He tells Dean that Sam was in Detroit when he assented to become Lucifer's vessel.

In the present day, Lucifer reiterates this to Sam, as he prepares to raise Death. He tells Sam that he will say agree to be his vessel "within six months. And I think it'll happen in Detroit."^{5.10 Abandon All Hope}