The Structures Survey was conducted in communities of more than five hundred people, and individual survey cards (see sample) were completed for more than 50,000 architectural properties. The survey identified architecturally interesting properties throughout Illinois. The properties are generally classified into three categories:
- Significant Individually
- Significant as part of a historic district
Properties were classified by their use or function, and information gleaned from signs, plaques, or cornerstones was recorded.
These survey cards are located in the Preservation Services Offices at Union Station, Springfield, Illinois.