At first, they thought it was caribou.

Whitehorse's Ivy Rudell and her husband were in their living room last week, when they spotted through their window something moving atop Golden Horn mountain.

"We took the binoculars and had a look and there was this thing up there," said Rudell. "It wasn't very clear."

golden horn mountain

The mysterious flag was spied on Golden Horn this week. Can you spot it? Try squinting. (Philippe Morin/CBC)

On Monday, Rudell decided to have another look.

"The light was perfect and I took the binoculars… and you could actually see the maple leaf."

Rudell said it "aroused a whole lot of curiosity."

How did this flag get on top of the estimated 1,700-metre-high Golden Horn? When? And why? Was it for Canada 150, Rudell wondered?

That's when CBC reporter Philippe Morin took to Twitter with Rudell's mysterious sighting.

Sighting up-close

It wasn't long before Wendy Shanks, a backcountry skier, offered up her story on spotting the flag up-close on the weekend.

"We usually try to get up there once a year in the spring… just because it is sort of a summit in our backyard," said Shanks.

It's a 23 kilometre hike up the mountain. One would have to go up Coal Lake Road through Mount Sima and find the "hard to see" ATV trail that seems to be moving away from Golden Horn, according to a Yukon hiking website. It would take approximately 6.5 hours to do the round trip.

golden horn mountain trail

"We didn't know it was there," said Shanks. "We could see sort of a red spot at the top of Golden Horn once we got out of the trees."

Up close, Shanks said it looked "fairly new". The flag was mounted on a "a well-built, two-by-four structure," she said

Shanks, too, had no answers, but guessed it was brought there by snowmobile.

wendy shanks

Wendy Shanks goes backcountry skiing on Golden Horn once a year. She spotted this flag this weekend. (Submitted by Wendy Shanks)

Social media solves mystery

When Shanks' photo was posted on the CBC Yukon Facebook page, Yukoners began to show interest — and pretty soon, they had some answers.

flag mystery whitehorse
flag mystery whitehorse
facebook mystery flag whitehorse

An 'epic' birthday trip

Turns out, it was a premeditated birthday mission that was years in the making.

"Ever since the first time I climbed Golden Horn, I knew I wanted to put a flag up there," said Donovan Cote. "I thought it would be a really patriotic thing to do."

After finally getting his hands on a large 14 by seven-foot Canadian flag, Cote and his buddies made a blueprint of the two-by-four structure to hold down the flag on the windy mountaintop.

"We did our homework."

Putting up a giant Canadian flag on Whitehorse's Golden Horn mountain0:21

With a drill in hand, his team "of crazy Canucks" hauled the wood and flag up the mountain on snowmobiles. The day was warm and sunny, said Cote, but it came with its challenges.

"Right before I got to the mountain, my engine blew on my Ski-Doo," said Cote. "But we ended up soldiering on."

donovan cote flag mystery

Cote (far right) and 'his boys' after they finished buildling the flag structure on top Golden Horn mountain near Whitehorse. (Submitted by Donovan Cote)

Mystery solved: "It was an epic last ditch effort to have an awesome sledding weekend with my buddies."

Cote says he is slightly disappointed that the flag is a mere black dot from the city, easily mistaken for a tree.

So it'll just be the "maple syrup on top" for those who make it to the peak, said Cote, who turned 32 years old last month.

"P.S. — happy birthday, Canada."

With files from Philippe Morin