As I wrote earlier, for most of human history, maps and charts were closely held state or commercial secrets. Making maps publicly available didn't really start occurring until the 19th century, Brown writes. It was only later that century that "the science of cartography reached maturity," he adds.
But even decades later, at the start of World War II, he relates, much of the world was poorly mapped. This touched off a search for forgotten maps in archives that might help fill in the blanks. "In the absence of anything better, a map published in 1880 or even 1860 was to be treated with respect," Brown writes. "Historical cartography suddenly became current and highly desirable."