We all live with maps, whether they are the mental sketches that direct us about our homes, our offices, and our towns, or the more complex and concrete documents that guide us on holiday trips or in our understanding of public affairs. From the earliest days of what is now Ontario, maps were one important means by which explorers, the military, the civil administrators, surveyors, and eventually individual settlers set down new information or pursued their business. Over time, however, these maps came increasingly to be overlooked as sources of information about our past. They were difficult to store, they...