Robert Berlo got hooked on maps at an early age. As a kid growing up in San Francisco he’d pore over roadmaps in the backseat of the car on family vacations. Sometime around age 11 he started collecting them.

By the time Berlo died in 2012 at 71 he’d amassed more than 12,000 roadmaps and atlases. But he did more than covet and collect them. Over the decades, Berlo spent countless hours mining his maps for data, creating tables, charts, graphs, and still more maps on everything from transportation systems to the population history of small towns. Now, Berlo’s collection is getting another life as a repository of previously hidden information.

“He was always the keeper of the knowledge,” says Berlo’s son Mark. When Mark was a boy, Berlo would plan out the best route for family trips and figure out the best places to stop for gas or get a bite to eat along the way. As an adult, while on trips with his wife and two sons, Berlo would type up index cards listing every town they’d pass along their route.

View Images Robert Berlo loved road trips and hiking. Photograph Courtesy Juanita Berlo

Berlo loved to take road trips, and he favored back roads to interstates, says his wife, Juanita. “He always had a set of maps in the car,” she says. “He could read them while driving and fold them back up while driving.”

When they weren’t traveling, the Berlos lived in Livermore, California. Robert worked nearby in the technical information department at Lawrence Livermore National Laboratory, first as an editor and later as deputy department head, putting his undergraduate degree in chemistry from MIT to work. “He was an extremely brilliant man,” Juanita says.

In the evenings after dinner, when other people might turn on the TV and mentally check out, Berlo would turn on classical music, sit at his desk, and work on his maps, often late into the night.

View Images Berlo kept extensive notes on MUNI routes and schedules. Photograph Courtesy Family of Robert Berlo

Juanita still lives in the couple’s mid-century house in Livermore. When I visited recently, she brought out a large envelope of her husband's maps and notes. Inside were neatly stacked timetables for MUNI, the bus and streetcar system for San Francisco, dating back several decades. There were sheets of MUNI route information torn from phone books and other sources, as if he’d been checking the official time tables against other listings. There were also many, many notes, both handwritten and typed, and a letter from a MUNI employee—apparently in response to a query from Berlo—describing how he could access historical information about routes and service.

View Images Berlo drew this imaginary map of a city on the north rim of the Grand Canyon. Photograph Courtesy Family of Robert Berlo

Juanita also showed me several maps of imaginary places Berlo had drawn. One showed a city along the shores of Mono Lake in eastern California. Another, which covered the top of a small table when we spread it out, depicted a sprawling metropolis along the North Rim of the Grand Canyon. Both had been drawn by hand on vellum in remarkable detail. The intricate street grids included neatly written names (some borrowed from Berlo's native San Francisco) and one-way traffic symbols. There were railroad lines, parks, creeks, and other features.

Mark Berlo thinks his dad drew these maps mostly for fun, like playing a paper and pencil version of the city-building video game Sim City in the days before video games. “When he drew a city, he drew it so it would function,” Mark says.

View Images This is a detail from Berlo’s map of the imaginary town of Millsburg, California, along the shore of Mono Lake. Photograph Courtesy Family of Robert Berlo

Berlo donated his map collection to Stanford University in 2011. The university also has several books he wrote and published himself. One of them, contained in a thick blue three-ring binder, sits somewhat incongruously on a shelf of cloth-bound books and atlases in the main library. The spine lists the title in large print: Population History of California Places. Inside are hundreds of pages of tables detailing the known populations of California towns and cities dating back as far as 1769, when the first Spanish mission was established in San Diego. The book, Berlo writes in the preface, is attempt to recreate the population history of every settled place that ever existed in the state of California.

Berlo wrote the book hoping to fill gaps in the population data collected by the U.S. Census Bureau. Before 2000, he writes, the Census didn’t count people living in smaller unincorporated places—that is, places without legally defined boundaries. Berlo tracked down population estimates listed in unofficial sources, including his vast collection of roadmaps and atlases. In total, the book contains population data on 5,500 California cities, towns, and other settlements, only 500 of which were ever incorporated.

Based on the preface, the work appears to be “an exemplary amateur history conducted in a very professional manner,” says Jon Christensen, an environmental historian at the University of California, Los Angeles. The accuracy of Berlo’s population estimates depends largely on the accuracy of his sources, Christensen says, but he adds that Berlo seems to have done an exceptionally careful job of documenting his sources and leaving a trail that amateur or professional historians could follow.

View Images This 1929 map from Berlo’s collection depicts Portland, Oregon. Photograph Courtesy The Robert C. Berlo Road and Street Map Collection, Stanford University

Meanwhile, Stanford political scientist Clayton Nall has been using Berlo’s map collection to study the politics behind the development of the U.S. highway system and to investigate how the expansion of highways may have contributed to the urban-rural divide in American politics. A team of research assistants has so far spent about 3,000 hours digitizing Berlo’s Rand McNally road maps, which go back to 1926. Once the maps are digitized and processed, they can be used for statistical analysis—to look, for example, at whether more miles of highway were built in counties that had more representatives in their state legislature, or whether urban areas with more extensive highway systems saw more white flight in the second half of the 20th century.

The statistical nature of Nall’s project probably would have appealed to Berlo. Many collectors collect maps because they find them beautiful or relish having a rare edition of an historical map. Not Berlo.

Mark Berlo occasionally tagged along with his dad to events for map collectors, and he says there was a big difference between his dad’s mindset and everyone else’s. “He wasn’t there for the maps,” he says. “He was there for the statistical information that was on the maps.”

View Images Berlo tacked this map to a wall in his home to keep track of how many times he’d visited each county in the United States. Photograph Courtesy Family of Robert Berlo

A few collectors were appalled by Berlo’s practice of stamping a blue serial number on every map he collected, Mark says. But the important thing to him was keeping track of all his maps in a computer database.