Generally speaking, maps can help genealogists get a feel for the cities, towns, or neighborhoods in which their ancestors lived and worked. For example, Sanborn maps show residential buildings, businesses, and civic buildings. Sanborn maps and other maps like it can help researchers answer questions like: What were the immediate surroundings of my ancestor’s home? Was it near the downtown center, or on the outskirts of town? Were there churches, theaters, or parks nearby? The answers to these and similar questions would provide additional context for your ancestor’s story.

Plat maps and Metsker atlases are valuable to genealogists because they “often contain the names of landowners, they predate topographic maps, and they show important historical township and county boundaries.”

Subsequently, historical maps can also help to confirm the past – and present-day – location of your ancestor’s home. For example, a city that was part of one Oregon county in 1890, may now be part of another. The original county may have disappeared altogether, and that land may have been allocated across several counties. Knowing the historic location of your ancestors home(s) can help researchers determine which County Clerk’s or Surveyor’s Office to reach out to for more information (e.g. for birth or marriage records, or property appraisal records, respectively).

Sanborn Fire Insurance Maps of Oregon, 1879-1956
The Sanborn Fire Insurance Maps of Oregon are an extensive collection of detailed maps of 178 towns and cities in Oregon prepared for the primary use of insurance companies. The bulk of the maps were prepared in the 1880s through 1920s. The maps depict both business and residential areas and provide detailed information about the location and type of construction of structures. Most of the maps are at a scale of 1 inch = 50 feet. The collection includes maps of Portland, Astoria, Bend, Corvallis, Eugene, Medford, and Salem as well as numerous smaller towns and villages. All types of structures are represented, including homes, apartments, and boarding houses; churches; schools, courthouses, community halls, parks, playgrounds, and other public facilities; warehouses, factories, mills, dryers, canneries, and creameries; retail stores, banks, and other businesses; and garages, barns, and sheds. The maps provide detailed information about lumber and saw mills and log ponds. Information about streets and railroads as well as the water system and fire department for each municipality are provided on the maps. The Sanborn Maps indicate the type of construction of each structure, whether it is wood, brick, stone, or a combination; the size of the structure and number of floors; and the heating source.

The Library of Congress has made a selection of their Sanborn maps available online.

Metsker's Atlases of Oregon Counties, 1929-1988
The Metsker's Atlases of Oregon Counties consist of 66 atlases and include one or more atlases for all 36 Oregon counties that depict property owners and donation land claims. The bulk of the atlases were published in the 1930s-1950s. Each atlas includes an index map. The number of maps per atlas varies from 20 to 300; however, most of the atlases have fewer than 100 maps. The maps are at a scale of 2 inches = 1 mile. In addition to property boundaries, the maps show roads; railroads; streams, rivers, and water bodies; and schools.

Central and Eastern Oregon Township Plats, 1858-1939
The Central and Eastern Oregon Township Plats consist of reproductions of the original manuscript plat maps for townships in regions of Oregon east of the Cascade Mountains prepared by the U.S. General Land Office and the U.S. Surveyor General; most of the maps were prepared in the 1870-1890s. Each township of 36 square miles is on a separate sheet. Most sheets have a scale of about 1:31,680 or 2 inches = 1 mile; the remainder are at a smaller scale of about 1.5 inches = 1 mile. These plats cover from Townships 4N to 41S and Ranges 6E to 37 E. Regions depicted in this collection include the Umatilla River basin, Blue Mountains, John Day River basin and tributaries, Snake River, Deschutes River, and Klamath Basin. Boundaries of the Umatilla, Malheur, and Klamath Indian Reservations are shown on the plats. Plats for the Vale and Owyhee Irrigation Projects prepared in the 1930s are included. Several of the plats show mining ditches and placer mining claims in the John Day River basin. The Klamath River, Klamath Lakes and associated marshes, Tule Marsh, and Modoc Lake as well as Fort Klamath and the Klamath Irrigation Project are depicted. The plats show section lines as well as natural features and vegetation such as prairie; timber, soil types; rivers, streams, sloughs, and wetlands; and fields. The maps include some topographic features. Most of the plats include a narrative description indicating if the township is appropriate for grazing or cultivation, the soil quality, availability of water, and type of timber. Wagon trails and military roads are shown on the plats as well as land claims. This collection consists primarily of single copies of each township plat; however, there are some townships represented by multiple copies of the same plat or different editions of the same township. These survey plats, as well as field note records for these townships, are available online through the Land Status and Cadastral Survey Records website prepared by the Bureau of Land Management's Oregon State Office.