Canadians amused by the improbable presidential run of Donald Trump might be surprised to learn the role their own country played in shaping his story.

Trump's grandfather started the family fortune in an adventure that involved the Klondike gold rush, the Mounties, prostitution and twists of fate that pushed him to New York City.

Friedrich Trump had been in North America a few years when he set out for the Yukon, says an author who's just completed a new edition of her multi-generational family biography.

​That Canadian chapter proved pivotal for the entrepreneurial German immigrant, says Gwenda Blair, author of The Trumps: Three Generations That Built An Empire.

"It allowed him to get together the nest egg he'd come to the United States for," the author and Columbia University journalism professor said in an interview.

"Whether he could've accumulated that much money somewhere else, in that short a period of time, as a young man with no connections, and initially not even English, is certainly ... unlikely."

He'd left Europe in 1885 at age 16, a barber's apprentice whose father died young.

Trump wanted a life outside the barber shop, far from the family-owned vineyards his ancestors had been working since they'd settled in Germany's Kallstadt region in the 1600s carrying the soon-altered surname Drumpf.

He sailed in steerage to join his sister in New York.

Within five years he'd anglicized his name to Frederick; moved to the young timber town of Seattle; and amassed enough cash to buy tables and chairs for a restaurant.

His next big move was heralded by the front page of the Seattle Post-Intelligencer of July 17, 1897, and its exclamatory headline: "Gold! Gold! Gold!"

It described a resplendent scene at the port involving mountains of yellow metal and men returning from the "New Eldorado" with fortunes as high as $100,000.

Trump sold everything and headed north.

A caravan of prospectors arrives at Chilkoot Trail to join the great Gold Rush. (Topical Press Agency/Getty Images)

The move to Canada spared him financial disaster. He not only sold off two Seattle eateries, but also land in nearby Monte Cristo, Wash. — right before floods and avalanches destroyed the nearby railroad and development plans for the town were scrapped.

Blair describes his perilous northward journey in early 1898.

After boarding a crowded ship to Alaska, Trump trekked over mountains, through Canadian customs, and to the Yukon River where he had to build a boat from scratch and transport a year's worth of personal supplies.

The worst was a notorious mountain pass. The U.S. National Parks Service estimates 3,000 animals died on the White Pass, with many bones still visible today in its so-called Dead Horse Gulch.

"Owners whipped horses, donkeys, mules, oxen, and dogs until they dropped. The bodies were not buried or even moved," Blair writes.

"Travellers ... had no choice but to walk over the remains. As the months went by, the walls of the pass were stained dark red from the blood."

Trump smelled opportunity.

He opened a canteen along the route, Blair says, where weary travellers likely stopped for a bite of Arctic roadkill. There are records for similar establishments along the route, Blair writes: "A frequent dish was fresh-slaughtered, quick-frozen horse."

This established a pattern for Trump's Canadian business model.

It's summed up in one chapter title: "Mining the Miners."

Unlike other gold-crazed migrants, Blair wrote, "[Trump] realized that the best way to get [rich] was to lay down his pick and shovel and pick up his accounting ledger."

'Liquor and sex'

In his three years in Canada, Trump opened the Arctic Restaurant and Hotel in two locations with a partner — first on Bennett Lake in northern B.C., and then moving it to Whitehorse, Yukon.

Their two-storey wood-framed establishment gained a reputation as the finest eatery in the area, Blair said — offering salmon, duck, caribou, and oysters.

It offered more than food.

"The bulk of the cash flow came from the sale of liquor and sex," Blair wrote. She cited newspaper ads referring obliquely to prostitution — mentioning private suites for ladies, and scales in the rooms so patrons could weigh gold if they preferred to pay for services that way.

He had made money; perhaps even more unusual in the Yukon, he had also kept it and departed with a substantial nest-egg. - Gwenda Blair, author

One Yukon Sun writer moralized about the backroom goings-on: "For single men the Arctic has the best restaurant," he wrote, "but I would not advise respectable women to go there to sleep as they are liable to hear that which would be repugnant to their feelings and uttered, too, by the depraved of their own sex."

The Mounties initially tolerated the rowdiness. There were exceptions, according to the legendary Canadian writer Pierre Berton. People faced forced labour or banishment from town if they cheated at cards; made a public ruckus; or partied on the Lord's Day.

"Saloons and dance halls, theatres and business houses were shut tight one minute before midnight on Saturday," Berton wrote in "Klondike Fever."

"Two minutes before twelve the lookout at the faro table would take his watch from his pocket and call out: 'The last turn, boys!"'

'I wouldn't call him a pimp'

Trump acted as cook, bouncer, waiter.

But Blair cautions: "I wouldn't call him a pimp."

She said backroom ribaldry was part of the restaurant package in those towns, and it's not clear how the arrangement worked: "As somebody trying to attract business to his restaurant, of course he would have liquor. Of course he would arrange easy access to women. A pimp is, I think, a different business model."

By early 1901, trouble was brewing.

The Mounties announced plans to banish prostitution, and curb gambling and liquor. Trump quarrelled with his partner. Gold strikes were getting scarcer.

"The boom was over, Frederick Trump realized," Blair wrote. "He had made money; perhaps even more unusual in the Yukon, he had also kept it and departed with a substantial nest-egg."

He returned to Germany with US$582,000 in today's currency, and found a wife. But he was greeted as a draft-dodger for being away and becoming a U.S. citizen during his military years.

So he was deported from his own country. He boarded a ship for New York, his wife pregnant with Donald's dad.

The elder Trump died of pneumonia in 1918, leaving behind some real estate. His son built the empire, his grandson the global brand.

Ironically, their heir is now running for president on a platform of mass-deportation. But Donald and grandpa share some traits — an entrepreneurial spirit, and formative youthful adventures in Canada.

Donald met his first wife, Ivana, at the Montreal Olympics.