Throughout history, maps have acted not just as guides to get a person from one place to another. They have also been used to define the world and to inspire explorers and adventurers to fill in the blanks.

Today in America, road maps – the fold-up kind that cost a few bucks at the gas station – are utilitarian. They show what roads will take a person from here to there.

But in the first half of the 20th century, road maps, especially their cover illustrations, did more than just show the way. They spurred motorists to take to the roads and explore. And they made sure you knew which gas to buy to fuel your adventures, and reminded you which oils and tires provided a smooth ride.

The spirit and salesmanship of these maps is on display in an exhibition, “Road Maps: The American Way,” at the Osher Map Library & Smith Center for Cartographic Education, in the Glickman Family Library at the University of Southern Maine. As part of the exhibition, on Saturday, there will be a series of four lectures “celebrating America’s love affair with the open road.”

The guest curator of the exhibition is Robert French, a retired geography professor at USM.

“I have an interest in antique autos, so I started to collect old road maps,” French said about the genesis of the exhibition.

Yolanda Theunissen, the map library’s curator, said that she had been “nudging him for years and years” to put the maps on display.

Her hunch was right. The exhibition, which opened in February, has turned out to be one of the library’s more popular shows, Theunissen said. “People can relate to it, in some cases people of a certain generation have actually used [the maps on display].”

The show is as much about the sensibilities the maps convey as it is about the routes they lay out. The maps and their covers “exuded adventure,” French said.

According to one of the exhibit’s labels, “The automobile road map is an American innovation and … a part of American culture. … Through both illustration and cartography, they manifest the changes in the American landscape resulting from the 20th century’s ‘auto-mobility.’ Their covers promoted a romance of the road that sold gas, oil, batteries, tires and other products. Most significantly, road maps created a core of American values based on the freedom of the open road.”

Sometimes their romantic vision went way beyond the basics of speed and freedom embodied in the automobile: “The mythic qualities of the open road allowed city dwellers access to the wilds of Nature. Rustic scenes and relic places awaited ‘rediscovery’ and exploration through the magic of the modern motor car,” according to exhibition literature.

One of the most striking images, from 1905’s “The Complete Motorist,” an image based on an earlier oil painting, shows a roadster barreling along a dirt road, dust billowing behind it, through wild forests and mountains as satyrs and centaurs high-tail it into the woods with nymphs in their grasps.

The exhibition notes that some maps inspired travel by showing roads that didn’t even exist. In the early decades of the 20th century, “to drive any distance was quite a feat,” French said. It wasn’t surprising that roads sometimes didn’t connect; trains were the dominant method of through-travel.

Often, the maps and their sumptuously colored illustrations offered city dwellers “a return to bucolic roots by way of a drive through the countryside” or “stressed the sheer excitement” of automobile travel.

The cover of a 1923 map distributed by the Go-Gas Co. used imagery that suggested stopping at its stations was akin to visiting Coney Island.

Many map covers used art deco illustration – solid, robust, curvaceous and brilliantly colored – to convey a soaring image of modernity, such as a Gulf “tourguide” map of Pittsburgh from 1947.

Other covers mimicked the style of the era’s top illustrators, reminiscent of children’s book illustrations from the 1920s and ’30s.

The exhibition notes that the cover of a Colonial-Beacon map from 1931 shows roads radiating out from the company’s emblem, like rays of light, to guide city drivers into the wilds of the country.

According to French, road maps underwent a “spectacular evolution” in the early 20th century.

Early road guides weren’t even maps; they were narratives describing a route.

Then there were “strip maps,” that showed a specific route from one place to another with minimal depiction of side roads.

“These can be very effective but if you get off the route you’re done for,” French said.

There were even “photographic auto guides,” which combined narrative directions, maps and photographs of intersections and landmarks to steer drivers in the right direction. These were very expensive to produce because they had to show both the going and coming perspectives, he said, and like strip maps were limited to a particular route.

Another drawback was that “They became outdated almost annually as the landscape changed,” French added.

Above all else, the most important thing about the maps handed out by oil companies at their gas stations was that “They were free,” French said.

And because they were free, they changed mapmaking.

Prior to the advent of the automobile, ordinary people never used road maps, they had no need for them, he said. “Maps were relatively expensive, so only the most powerful people needed them. But now everybody needed them.”

This led to the “democratization of cartography,” according to French, something that is “very American and very apropos to the freedom of the road.”

While maps pertaining to Maine are scattered throughout the exhibition, one display is specifically dedicated to “Mapping Baxter Park.”

French traces the history of the park through a series of official Maine highway maps, starting with a 1932 version and ending with the 2000 edition. The maps show the expansion of the park from its original 6,000-acre parcel to its current size of 202,000 acres.

This section of the exhibition also underscores the change in cartographic information provided on road maps. The 1932 map shows roads, towns, tracks, lakes, rivers, campsites and Mount Katahdin. The 2000 edition shows those features plus all the other mountains in the area plus their elevations, recreational activities, such a cross-country skiing, locations of outdoor outfitters, dams, gates and public reserve land, as well as the park.

Even the covers of the maps show a historical change of perspective. The 2000 edition shows West Quoddy Head Light, as well as cultural, recreational and wildlife scenes, telling what the map is going to lead you to.

The 1932 map shows that you can get there from here by car. The cover has a soaring view of the Waldo-Hancock Bridge over the Penobscot River.

In conjunction with the exhibition, four lectures on “Celebrating America’s Love Affair with the Open Road” are scheduled from 9 a.m. to 1 p.m. Saturday in the Woodbury Campus Center at USM. The speakers and topics are James Akerman of Chicago’s Newberry Library who will talk about road maps and consumers; guest curator Robert French who will talk about National Highway Association maps; Arthur Krim of the Boston Architectural Center and the Massachusetts Historical Society who will talk about cartography on U.S. Route 66; and Kathleen Shea of the Maine Historical Society who will talk about U.S. Route 1 in Maine.

The exhibition is open 12:30 to 4:30 p.m. Tuesdays through Thursdays, 6-8 p.m. Wednesdays and Thursdays and 9 a.m. to 1 p.m. Saturdays through Dec. 20. Registration for the lectures costs $10 and includes refreshments. For more information and to check on seating availability, call 780-4850.