The Illinois Rural Survey began in the summer of 1979 when the first counties were surveyed in a pilot project conducted by the state office. All structures built prior to 1945 in unincorporated areas of St. Clair, Madison, and Monroe counties were photographed and their physical characteristics recorded. A total of 4,619 sites were identified. This building-by-building approach ensured that all historic properties were evaluated, not just a select group as in the earlier surveys. Structures were classified according to vernacular and high-style building types developed especially for the survey. Small black-and-white photographs were attached to 5-by-7-inch cards that recorded basic information on building materials, function, alterations, and construction date. Since 1979 rural properties in a total of 24 Illinois counties have been surveyed. Rural surveys are a high priority in counties where resources are being lost due to development, or where the majority of the historic resources are in rural areas. Counties in the St. Louis and Chicago metropolitan areas were targeted first, and in the early 1980s, surveys of Illinois' five southernmost counties were completed by the Southern Five Regional Planning Commission. The most comprehensive rural survey was of Kane County, where information on more than 5,500 sites was collected in 1986 and 1987. Many farmsteads were individually mapped, and the settlement pattern of the unincorporated areas of the county was researched through historic plat maps and atlases, county histories, and interviews.