By the late 1920s, American aviation strip charts were considered among the best in the world for cross-country flying along established airways, but Charles Lindbergh’s epic trans-Atlantic flight in 1927 followed by his tour of the United States popularized flying, and laid the foundation for general aviation, which required a new type of aeronautical chart designed for area or regional use rather than airway flying. The first mapping organization to meet this need in the United States was the Rand McNally & Company of Chicago. Rand McNally state road maps were already well known to pilots, which they dubbed “Rand McNally Navigation.” Its popular Pocket Road Map series coincided with the post–World War I cross-country flying craze, was national in scope, inexpensive, and depicted features of particular interest to pilots for visual flying, such as rivers, terrain features and railroads.
Sensing new customers when market surveys began showing that more flying was being done off of established airways than on them, Rand McNally introduced its “Standard Indexed Map Series with Air Trails” in late 1928 following two years of research, experimentation and flight testing. It was the first American air navigation map series that provided coverage for the entire country.
The base map was Rand McNally’s standard state map, which appeared on the verso and was already familiar to both map dealers and aviators. It was constructed on the Lambert Conical projection, an ideal projection for plotting compass courses and radio bearings.
Air navigation data, overprinted in red type and symbols, was clearly displayed and easy to interpret. Basic flight information included mean magnetic courses along established airways, beacon lights, locations of airports, radio directional beacons and, topographic elevations, and lines of equal magnetic declination. Printed tick marks bordered the map at ten-and fifty-mile intervals to aid scaling and interpreting distance.
A small pocket-size airport and city directory accompanied each “Air Trails” map. It included a short eight-page treatise on “Elements of Practical Air Navigation” written by Thoburn Lyon, a former U. S. Coast and Geodetic cartographer. Lyon later expanded this major innovative contribution to the fledging aircraft industry into a major publication titled Practical Air Navigation, which was issued by the Department of Commerce. More than 1.5 million copies were sold in numerous editions over a thirty-year span.
Rand McNally’s Air Trails Maps series provided the best national coverage for air navigation from 1928 until about 1935, but it could not compete with the U. S. Coast and Geodetic Survey’s Airway Section’s “Sectional Aeronautical Chart.” Lyon rejoined the U. S. Coast and Geodetic Survey in 1933, and later headed its aeronautical chart division.