Flashes of light pulse through the dark, a repetitive rhythm transmitted in Morse code, marking a path in a void.
One by one, each letter from the string WUVHRKDBGM — whose logic is visual, building predictably from dashes to dots and back again, rather than alphabetic — one by one, each signaled letter beams at many millions of candlepower from beacons 51 feet high, one beacon every ten miles, strung across the U.S. from New York to San Francisco:
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Ten flashing bits of code, for which the pilots pioneering transcontinental U.S. airmail made a mnemonic: “When Undertaking Very Hard Routes Keep Direction By Good Methods.” This simple system is what made coast-to-coast airmail viable in the decades after World War I.
Flight became an obsession in the United States in the 1920s, and Icarian daredevils dreamed of flying higher, farther, faster. Charles Lindbergh winged his solo way nonstop from New York to Paris aboard the Spirit of St. Louis in 1927. The next year, Amelia Earhart became the first woman to cross the Atlantic, going on to set a slew of other records and then vanishing in the South Pacific. The obsession kept pace with technological development, and it was only 20 years later that Chuck Yeager shattered the sound barrier. Two decades after that, Neil Armstrong and Buzz Aldrin made the leap to the moon. You know their stories, have seen their photographs — modern myths of humans turned into heroic machines.
But humbler dreamers also wanted quick, long-distance communication: the transplant to another town, yearning for a word from home; the businessman, eager to conduct his affairs at the speed of flight. So it was perhaps inevitable that the mail would take to the sky, and the first experimental U.S. Mail flight occurred in 1911, when pilots delivered letters from Garden City, New York, to nearby Mineola — a distance of one-and-a-half miles. A success.
In 1920, after faster planes had proven reliable over ever-greater distances and a few rounds of Congressional funding had established an official U.S. Airmail service, a truly long-haul route was opened between New York and San Francisco. Even so, it wasn’t much faster than the older train delivery. A locomotive could chug 24 hours a day, but no one flew at night. To do so was suicidal. Aviation instruments were rudimentary — there was no GPS, no radar, no in-plane radio — and pilots couldn’t see in the dark. And so, beginning in the first years of the decade, the Post Office (and later the Department of Commerce, once the service was transferred to its jurisdiction) built an enormous infrastructure, a ground-based constellation. More than 1,500 beacons, developed by GE, Westinghouse, and Sperry Gyroscope, along with towers, searchlights, emergency landing fields, refueling stations, lighted wind vanes, and 56-foot-long concrete arrows laid into the earth and lit by flickering acetylene lamps on an 18,000-mile network of flight paths.