35 ILCS 200/3-55

Staffing of county assessor's office - Counties of 3,000,000 or more. The county assessor in counties with 3,000,000 or more inhabitants shall appoint one chief deputy assessor, one deputy assessor in charge of administrative service division and one deputy assessor in charge of real estate division. The county assessor may also employ other clerical help and deputies as may be necessary, each one of whom (except the chief deputy assessor, deputy assessor in charge of administrative service division, and deputy assessor in charge of real estate division) shall be appointed by the county assessor under the civil service law applicable in such counties.