A hundred years ago this month, the April 1921 issue of Popular Mechanics described the radio network of the U.S. Post Office Department. At a cost of $26,000, the post office had put together a string of 15 stations–10 owned by the post office, and 5 others shared with other government departments–to facilitate the carrying of airmail across the country.

65 airplanes were in use transporting 200,000 letters daily, and to manage the system and provide meteorological data, radio was necessary. The first one, shown here, was established at College Park, MD. Others were at Bellefonte, PA, St. Louis, MO, Omaha and North Platte, NE, Cheyenne and Rock Springs, WY, Salt Lake City, UT, and Elko and Reno, NV.

Work on the system had begun in 1920, and at press time, sixteen radio men were in the employ of the department. Plans were in the works to equip planes with radio direction finding equipment and radiotelephones.