Perhaps I don't understand your question. Motorists used the cross-country highways of the time.

All-weather roads crossed much of the nation by the mid 1930s; the system of numbered US highways had been introduced in 1926. Prior to that, "named highways" like the Lincoln Highway or Yellowstone Trail had signs directing you from town to town coast to coast or border to border. By 1940, even most state highways were paved, meaning you could reach almost any town in the country.

The first arduous cross-country journeys were made in the teens, but by the late 1930s it was commonplace for a middle-class family to make an auto trip of several hundred miles to vacation in a national park or to visit relatives. In The Grapes of Wrath, Steinbeck writes about the cross-country journey made via U.S. 66 by hundreds of Okies to California, looking for work.

Old road atlases and state highway maps showing the extent of the highway network are easy to come by, and some are even online through the David Rumsey Collection. Many state highway departments have scans of their highway maps, dating back to the 1930s, on their websites. Wayfinding was certainly trickier in the pre-Interstate era, requiring motorists to keep an eye peeled for a small sign (sometimes missing from the pole) indicating a turn onto an intersecting city street or section-line road, and jokes and cartoons were commonplace about the hapless wife trying to interpret (or refold) the road map while being hectored by the husband behind the wheel.

As for the on-the-road experience, books like George Stewart's U.S. 40 or N.A. 1 give one kind of insight, while literary works like Steinbeck's Travels With Charley or Kerouac's On the Road give another kind. Guides to the lost landscapes of U.S. 66 are still big business: Michael Wallis's Route 66: The Mother Road or Tom Snyder's Route 66 Traveler's Guide. Contemporary glimpses into cross-country motoring, especially in the scenic Intermountain West, can occasionally be found in Holiday or even National Geographic.