​This Guide describes records of the Territorial and Provisional Governments in the custody of the Oregon State Archives. It includes records of counties created before statehood, administrative histories, traces the development of offices and public bodies and explanations of official duties.

Inventory for each county and office is arranged alphabetically by series title. Each series description includes a title and a description of how records are used (function); types of records included in each category (physical content); type of information found (informational content); significant changes to format, creator, or content; inventory cut-off dates; and restrictions a category may have regarding public access. Organization of offices and functions, the contents of the records, or format of records may vary. Notes are included to indicate differences.

Records are listed alphabetically by the exact title printed on the volume cover or on the box label, if the records are stored in records containers. Where information is inaccurate, illegible, or missing project staff provided suitable titles within brackets [ ]. Each record's title is followed by file, case, or volume numbers and dates. The size or amount of records is listed in parenthesis. Records stored in boxes or file cabinets are measured in cubic feet; books or volumes and reels of microfilm are counted; sheets of microfiche are measured in linear inches or feet; maps, drawings, and photographs may be counted or measured in cubic feet.

Series descriptions follow USMARC-AMC standards and include series title, range of dates, volume in cubic feet, and a description of information in the series. Each description is identified by a series number. Descriptions include a microfilm reel number and database record number.

County histories trace the establishment and evolution of the 27 county governments of Oregon Territory. These include information on the founding of the county; the designation of county boundaries; the location of the county seat; construction of the county courthouse; the development of the county government; and a description of the major industrial geographical, demographic, and/or historical features of the county. These histories also include Washington counties which originated as part of the Oregon Territory. Washington Territory was created March 2, 1853 and absorbed 8 of Oregon's original counties.