WHITEHORSE, Yukon Territory—Denis Jacob has been staking claims for gold-company clients since 1975. But he's never seen a frenzy quite like the one playing out in the Yukon—Canada's western-most territory and the site, more than 100 years ago, of one of history's greatest gold rushes.

Mr. Jacob is part of a small, secretive band of "stakers," who hike miles at a time across the territory's mountains and forests, hammering wooden stakes into the ground. For years, they've quietly marked off and registered land for mining...