In the past, maps have been used only to illustrate texts or to buttress views gleaned from more traditional written sources. However, maps are primary sources and should be integrated with historical research from the outset. They should be viewed as true documents, not as secondary sources.
"Short Subjects: Map Management for Small Collections,"
Provenance, Journal of the Society of Georgia Archivists
Available at: http://digitalcommons.kennesaw.edu/provenance/vol8/iss2/5