An obsessive cartographer in Reif Larsen’s novel, The Selected Works of T.S. Spivet, describes a 25-year project of attempting to compile and catalogue maps of all kinds to arrive at “a totally comprehensive understanding of the history, geology, archaeology, botany, and zoology of the land.” Mr. Benefideo realizes that the task is too much for one person or even one generation and hopes that a new generation of cartographers will pick up where he left off. “A map does not just chart,” he suggests, “it unlocks and formulates meaning; it forms bridges between here and there, between disparate ideas that we did not know were previously connected.”

Maps are among the best tools available for historical analysis, much as charts and graphs are essential to science. They come in many varieties. Good maps are a graphic, succinct summary of information, fertile with potential applications that may never have been predicted by their creators. This article summarizes how maps, and closely related documents, have been used in innovative ways by visitors and staff at three archival repositories where the author has provided reference services.