For an African-American who wants to break into politics Chicago and Atlanta are obvious choices. You certainly don't go to Portland or Seattle or Phoenix.
Chicago and Atlanta aren't as hopelessly run down as many other big cities, and Blacks have a clearer shot at the political prizes than they do in NY, LA or SF, where other groups have dibs on offices.
And the chances of going statewide are much better in Illinois than in Georgia. Not for nothing were the first post-Reconstruction Black Congressmen from Chicago (as well as the first African-American Democratic senator - Carol Moseley Braun).
Plus, if you're looking for a career in Democratic politics and you get a summer job offer from the law firm where Adlai Stevenson's old law partner and Kennedy's FCC head (Newton Minow) works, you take the job.
I might agree with that. Obama pursued Chicago because he was already interested in going into politics.
I am also interested in the reports that Alwaleed Bin Talal may have underwritten the cost of his some of his education at the suggestion of Khalid al-Mansour. If that is the case, then some one other than just Obama may have had an interest in seeing him installed in Chicago.