AGE: 57 OCCUPATION: Alderman, 40th Ward

The City Council floor leader is “by far the alderman whose advice the mayor trusts,” says one City Hall insider. At Emanuel’s behest, O’Connor will chair a powerful new committee overseeing contracts with the city’s union employees.

RELATED: Most Powerful Ex-Chicagoans | Power Couples | Power Siblings | Up-and-Comers | Poll: Which Powerful Chicagoan Would You Call Back First? | Quiz: Do You Know Chicago’s Power Players? | Back to all 100

Photograph: City of Chicago