Minnesota’s Great Hinckley Fire of September 1894 had warned of the size, intensity and speed that drought-parched forests can incinerate, particularly when loggers leave vast slash piles and other debris in their wake.
More than 400 people died in that conflagration, including apparently, for the trivia-minded, Thomas P. “Boston’’ Corbett, the Union soldier who killed John Wilkes Booth, President Abraham Lincoln’s assassin.
Not many years later, forest fires in Idaho, Montana and Washington consumed 3 million acres of virgin timber, killing 85 people.
In response, by the late 1930s, more than 5,000 fire towers had been built nationwide.
In Minnesota, the towers replaced “tree lookouts’’ that were little more than boards placed high atop pines or other tall trees that offered critical vantage points. And fire towers here generally were more statuesque than those in Western states, where shorter lookouts could be erected on mountaintops and other lofty vantage points.
“Also, towers out West often had beds in them and some sort of small living quarters,’’ said David Quam of Bemidji, who has been fascinated since childhood with fire towers. “In Minnesota, a cabin often sat at the base of the tower, or near it, where lookouts lived when they weren’t watching for fires.’’
Tinder dry as northern Minnesota is now, the region’s most dangerous fire season usually is spring.
That’s when snow melts, leaving a vast landscape of dry grass beneath bare-limbed trees; conditions that are ripe for fire, particularly on hot, windy days with low humidity.
In peak fire seasons, DNR and Forest Service pilots, and contract pilots, often crisscross the northern part of the state, looking for fires and using precise Global Positioning System (GPS) coordinates to report smoke or flames.
More primitively, a century ago, tower lookouts in some parts of the country reported fires in Morse code, using a heliograph, a device that reflects sunlight in two mirrors.
Later, two-way radios were used.
But spotting fires was only part of a lookout’s job: Pinpointing their locations also was important. Aiding that effort in 1911 was an invention by William Bushnell “Bush’’ Osborne Jr., a young Forest Service employee stationed in Oregon.
Osborne’s brainchild, an alidade — or Osborne Firefinder, as it also came to be known — allowed lookouts to determine exact compass readings of smoke detected from their towers.
Continually refined by Osborne over the next 25 years, the invention remains the most widely used fire plotting instrument in the world, according to the Forest Service.
“In Minnesota, when we had a lot of towers Up North, lookouts in three different towers could sometimes spot the same fire and, working together, triangulate its exact location,’’ said Curt Cogan, DNR forestry enforcement coordinator stationed in Brainerd.
“Today, with everyone having cellphones, most of our fire detection comes from the public,’’ Cogan said. “Even the aircraft part of fire surveillance isn’t used as much as it was even five years ago. Flying aircraft is expensive, and oftentimes we hear of fires from the public even before pilots report them.’’
In at least a handful of Western states, where cellphone reception can be problematic in mountainous areas — decreasing the chance citizens can report fires — cameras and high-tech smoke-recognition software are being employed, further reducing the need for human lookouts.