The Oversize Collection consists of unbound items from various Regional History Center collections which are too large to store in regular archival boxes.

The Oversize Collection contains five major groups of documents: posters and broadsides, photographs and prints, maps, newspapers, and certificates.

The Embree Collection's railroad calendars and posters show the locomotives of various railroads from the late 1930's through the mid-1950's. The war poster collection contains 629 posters from World Wars I and II depicting recruiting, morale, propaganda, and production incentive. A pdf of the item level inventory of the World War I and II posters can be found in the inventory. Due to the fragile condition of these posters the researcher will view the color slide reproductions instead of the actual posters.

Oversize photographs and prints include scenes of northern Illinois and local residents.

The collection of regional maps includes nine pre-1832 maps of the Great Lakes region from the Nelson Collection and sixteen maps of Illinois from 1835-1911 showing the development of Illinois counties. There are also special purpose maps concerning Illinois rail lines, coal fields, highways, and climate. Maps of DeKalb show the development of the county and city from the 1842 forward.

The collection of newspapers is maintained for use in exhibits and provides front pages for such things as the Pearl Harbor attack, the Chicago Fire, the ends of World War I and II, the Kennedy Assassination, the Chicago Bears Super Bowl title, and so on. DeKalb city and county special anniversary issues are also available here.