The School District Data Book (SDDB) is a database and information system housed on 51 CD-ROMs containing the most extensive set of data ever developed on children, their households, and the nation's school systems. The Data Book allows comparisons among school districts and permits the extraction of data about districts with particular characteristics. The database provides up to 200,000 data items for each school district or county, and a mapping feature enables users to view maps of all individual school districts in the nation for the first time. Approximately 15,000 school districts have been mapped. These are usually the same districts included in the Common Core of Data. This briefing document is organized into the following sections: (1) development of the SDDB; (2) features of operation and software; (3) database content and applications; (4) mapping features and applications; and (5) school districts and the mapping project. (SLD)