Observation and experiment are seen as the cornerstones of empirical science. Astronomy, an inherently observational science, affords a case study of a discipline in which controlled experiments cannot be performed. The author argues that in such disciplines maps and mapping serve to interpolate intellectually between observation and experiment. This is particularly noticeable in the early conceptions of cosmos and changes in worldview wherein major cognitive shifts are encoded in maps. With historical advances in map-making techniques, the epistemic purposes served by maps have also evolved significantly. Maps in astronomy today are deployed as powerful visual devices that record and transmute observational data to support theoretical ideas underpinning our current understanding of the cosmos. One example is dark matter maps, which offer compelling indirect evidence for the existence of the elusive dominant matter component that shapes our universe: dark matter.