County atlases will be most useful for looking at rural properties of about 10 acres and larger. But they also often provide detailed street plans of cities and villages without ownership information. Atlases published before 1920 were generally big fancy hand-colored affairs. Starting in the 1920s they shrunk dramatically to simple black and white booklets. Today, county plat books are usually published by either Rockford Map Company or Farm & Home, but with county governments developing their own computer systems, plat atlases may be self-published instead. Since about 1955, atlases are generally issued every 3-5 years but there is no strict schedule. The MSU Map Library tries to collect every Michigan county atlas ever published. The collection is not complete. The Library of Michigan in downtown Lansing also has an excellent collection.
The atlases vary in features depending on the publisher. All county atlases will mark the boundaries of rural properties, note the owner of the land, and the acreage of the plat. Most atlases will also note the location of schools with a small drawing, and residences with a small black square. Some atlases provide further detail such as the location of barns and other outbuildings, photographs provided by 'subscribers' and directories of local residents and businesses.