Sentence:  He was also at this time , although not so interwoven in high politics and the rackets as Torrio and Capone , the most powerful and most dangerous mob leader in the <WSD>Chicago</WSD> underworld , the roughneck king . 
Meaning of the word marked with <WSD> tags:  largest city in Illinois; a bustling Great Lakes port that extends 26 miles along the southwestern shoreline of Lake Michigan