DeKalb County Treasurer City, County & State Government DeKalb County Treasurer Visit Website 110 East Sycamore Street Sycamore, IL 60178 (815) 895-7112 (815) 895-1695 (fax) Facebook Hours: Monday - Friday 8:30 A.M. - 4:30 P.M. Except holidays About About The DeKalb County Treasurer serves as both Treasurer and Collector for DeKalb County. As Collector, the Office prepares bills and receipts for the collection of real estate taxes, drainage taxes, and mobile home taxes within the county.