Matthew Unrein is the City Administrator for the City of Arnold. The City Administrator is appointed by the council with the consent of the mayor and is the chief administrative assistant to the mayor.

The City Administrator has general supervising control of the administration and management of the governmental business and employees of the city. He or she shall appoint and discharge all department heads and employees of the city except elected officials or persons appointed by the mayor and council.

The position involves establishing and interpreting policy approved by the council, as well as offering advice to aid council decisions.