United States Census Bureau and Indiana Geological Survey
The following is excerpted from an online document produced by the U.S. Census Bureau pertaining to unified school districts (found at http://www.census.gov/geo/www/cob/sd_metadata.html): "School districts are geographic entities within which state, county, or local officials provide public educational services for the area's residents. The U.S. Census Bureau obtains the boundaries and names for school districts from tate officials. The U.S. Census Bureau first provided data for school districts in the 1970 census. For Census 2000, the U.S. Census Bureau tabulated data for three types of school districts: elementary, secondary, and unified. Each school district is assigned a five-digit code that is unique within state. School district codes are assigned by the Department of Education and are not necessarily in alphabetical order by school district name."