With 150,000 or so old print maps to his name, David Rumsey has earned his reputed place among the world's "finest private collectors." But the 69-year-old San Francisco collector doesn't have any intention of resting on his cartographic laurels. He continues to expand his personal trove as well as the digitized sub-collection he makes open to the public online — some 38,000 strong, and growing.

"I'm pretty old for a geek map guy," he says. "But I stay young by embracing new technologies all the time."

Rumsey, a native New Yorker, began his career teaching and practicing art — specifically, its intersections with technology — before getting involved in a charity on the West Coast. After starting his map collection Rumsey used that early art-tech interest to stay ahead of the digitization push. He's created a series of interactive maps that layer old prints onto the Google Earth and Google Maps platforms, and this summer he plans to launch a geo-referencing tool (similar to one recently introduced by the British Library) that lets users get involved in the digital mapping process themselves....