Kruzof Island is in the north Pacific Ocean, one of many Alaskan islands which run down what would otherwise be the Canadian coast line, and not too far from the state capital, Juneau. Kruzof Island is home to Mount Edgecumbe, a dormant volcano stretching about 3,200 feet to its summit. Mount Edgecumbe is a tourist attraction — it makes for a managable hike and is generally safe. The most difficult part about climbing the mountain is getting to it in the first place — Kruzof Island does not have a permanent human population, and therefore, there are no regular transports to the mountain. The closest town, Sitka, Alaska, is on a nearby island. To climb Edgecumbe, one typically leaves from Sitka.

In general, placing a city nearby a volcano is a bad idea, but Edgecumbe has been dormant for millenia — its last known eruption was over four thousand years ago. But in 1974, the town of Sitka got a scare. Edgecumbe, apparently, started to awake from its long, long slumber, as seen above. On the first day of April of that year, a plume of black smoke appeared, rising out of the top of the mountain. Conditions in the area were unusually clear, and people from Sitka could easily see the now-festering volcano. Was Edgecumbe no longer dormant?

The Coast Guard went to check, dispatching a helicopter to fly over the volcano’s crater and check for — well, who knows? What the helicopter pilot saw, though, was not an eruption. Rather, it was a message in the snow, spray painted in large black letters:

“APRIL FOOL”

Sitka was the target of an extravagent prank.

The prankster’s name was Oliver Bickar, better known as Porky to his friends and family. The middle aged man came up with the idea in 1971 — three years earlier! — and started preparing. He collected dozens of old tires in an airplane hangar and waited. The conditions were near perfect on, coincidentally, April Fool’s Day 1974. He convinced some friends (and a helicopter pilot) to help him transport his collection of tires to the mountain’s summit, douse them all in kerosene, and light them on fire. He even went to the trouble of getting clearance for his prank from the FAA and local police — just to make sure that they didn’t get arrested for their harmless prank, and to make sure local officials could prevent a panic outbreak. (They forgot to or negligected to inform the Coast Guard.)

Not only did Bickar not get in trouble for his prank, but, as recounted by the Muesum of Hoaxes, he actually got a lot of good press about it and positive reactions from locals. Even a Coast Guard admiral congratulated Porky on a prank well pulled.

Bonus fact : Juneau, Alaska is only accessible by air or sea — all cars and trucks in the city are brought in on barges or ferries. Road construction and maintenance is expensive given the environment of the area. None of Juneau’s roads leave the city.

From the Archives: November Fools: Another contender for greatest prank, ever.

Related: Make your own volcano.