The MacDonald Pass airway beacon was the last of eighteen beacons constructed across western Montana as part of the Northern Transcontinental Airway’s New York City to Seattle airmail route. The ninety-one-foot-tall, steel structure held a revolving, one-million-candle-power beacon originally encased in a glass dome. Red and green directional lights attached to the tower indicated the route, while flashing red course lights identified the beacon in Morse code. Gas-powered generators powered the beacon until circa 1942 when it was connected to electrical lines. Before the advent of radio navigation, airway beacons served as a critical nighttime navigational aide, guiding pilots along routes between airports. From 1926 to 1938, the U.S. Bureau of Air Commerce created 18,000 miles of airway corridors and installed 1,550 airway beacons to mark the routes for night flying. In Montana, the International Derrick and Equipment Company of Columbus, Ohio, fabricated the towers, which were paid for with funds from the Works Projects Administration. Construction of six beacons between Bozeman Pass and Helena and twelve beacons between Lookout Pass and MacDonald Pass began in February 1935. When the Civil Air Administration lit this beacon in November 1935—completing Montana’s system—over 4,000 people braved frigid weather to attend a celebratory event at the Helena airport. Though most of the country’s beacons were replaced with ground-based radio stations by the mid-1970s, Montana’s private pilots successfully lobbied to keep seventeen beacons lit through 2017. As of 2021, several adopted beacons still light the night sky, recalling Montana’s aviation heritage.