One of the most spectacular pieces in his collection of some 1,000 maps shows an enormous, roughly triangular island hugging the western coast of a continent called Nova Granada, below a land simply labeled "Terra Incognita." Although this island–actually California–did not exist in 1666 when Dutch cartographer Pieter Goos printed the map, it was a widely popular theory, persisting on maps of North America until the 18th century.

TOP: A rendering by French mapmaker Nicolas de Fer depicting California as an island, ca. 1720, listed for $35,000 at the Arader Gallery in New York. Above: The Library of Congress has completed the $10 million purchase of the only known copy of the 1507 world map by Martin Waldseemüller, a section of which is shown. (W. Graham Arader III; Geography and Map Division, Library of Congress)

Now that there are no more blank spots on the globe, and GPS receivers can pinpoint our locations within a few feet, it may seem strange to the uninitiated that outdated maps of an illusory island would be worth much. But prices are skyrocketing. A rendering by French mapmaker Nicolas de Fer from 1720 listed for $35,000 at the Arader Gallery in New York.

To McLaughlin, a former financial executive and Air Force pilot, this makes perfect sense. Over the past three decades, he has built what is arguably the world’s most comprehensive collection of such maps, worth about $1 million. Like many serious collectors, McLaughlin scorns what he calls "pretty maps" in favor of those with historical significance. The maps in his collection illustrate the acquisition of knowledge over the course of more than 100 years, and like other hardcore cartographiles, he has a fondness for maps of his home turf–California, a state that, despite plate tectonics, remains firmly attached to North America.

"I used to go to private dining clubs in New York, and we’d just see scenes of English people fox hunting. This is an alternative to that, very much a California alternative," McLaughlin explains. "You have the ability to trace the progression of not just the island out in isolation, [but] North America from the East Coast on through."

The antique maps that now command thousands of dollars on the auction block have always been extremely valuable. In fact, during the reigns of Philip II and Charles V of Spain, printing and disseminating a map without the king’s permission carried a penalty of death. Maps, laborious and time-consuming to create, served as both a tool to advance power through trade routes and a means to articulate that power by claiming undiscovered lands. The naming of a territory is considered so important that the Library of Congress spent $10 million in 2001 for a 1507 map by Martin Waldseemüller featuring the first known reference to America–the highest recorded price for a single map.

Thanks in part to New York—based dealer W. Graham Arader III’s efforts to popularize the trade over the last 30 years, today there is a small but thriving American market for antique maps. It is a clubby world, where major collectors know one another and map conventions attract only a few hundred faithful.

Fueled by demand from serious collectors, as well as interior decorators, prices have risen steadily over the past two decades. For example, a popular world map by legendary English cartographer John Speed, which fetched £1,500 ($2,000) at auction at Sotheby’s in London in 1984, commanded £7,000 ($12,600) last year. Early maps and atlases were rare luxury items when originally produced, and few have survived. New York—based collector Eric Goldstein believes the market has been fueled lately by low interest rates. Goldstein, a financial executive, claims he can expect an 8 to 10 percent annual return on a map, while enjoying ownership of a fascinating work of art.