United States voters who wish to learn more about how presumptive Republican presidential candidate Donald Trump made his fortune, which he claims to be valued at billions, should start with historian Gwenda Blair’s book “The Trumps: Three Generations That Built An Empire.”

According to Ms. Blair’s book, the recent generations of the Trump family made money the old fashioned way: by means of inheritance. There is an interesting rags to riches story, however, and it features prostitution in Canada and how the elder Friedrich Drumpf took advantage of it.

In a September 2015 report about Ms. Blair’s book, Alexander Panetta of The Canadian Press explains that Donald Trump’s grandfather was a brave German immigrant who set off for the United States after losing his gather as well as facing hardship and poverty.

The Drumpf family was known as a close-knit clan that owned modest vineyards in Kallstadt. Friedrich was not the first Drumpf to become a German immigrant in the United States; he joined his sister in New York in the late 19th century.

Young Friedrich’s family name would soon be Anglicized (or Americanized, if you will) to Trump. He set off for Seattle during the Gold Rush, and he followed others north to Canada, where the Yukon region promised even more of the precious metal.

The elder Trump certainly had greater business acumen than his grandson Donald. In Seattle, he quickly set up two cafes that served cheap and hearty meals to gold seekers. He sold those two businesses when he moved to Canada, where he opened a canteen for those who traveled on the inhospitable Gold Rush trail. Trump sold roadkill, liquor and offered rustic lodging.

Later, Trump would reinvest profits into the Arctic Restaurant and Hotel in Yukon. Initially, the Arctic Restaurant was located in British Columbia, where it was mostly a family diner. By the time Trump moved to Yukon, the establishment improved its menu to offer caribou, oysters, salmon, whiskey, and lots of sex.

According to Mrs. Blair, Trump’s Arctic Restaurant and Hotel in Yukon rented private suites for ladies only. Each room was equipped with a scale in case a miner wanted to pay for sexual services in gold.

Trump was a hard working man at the Arctic Restaurant. He cooked, served meals and even acted as security guard. He was discreet about the prostitution side of his business and did not allow rowdiness for fear of the Royal Canadian Mounted Police showing up.

After the Gold Rush, Trump quietly shuttered the bordello and took his profits -valued at half a million dollars- back to Germany, where he quickly found a wife. It so happened that he missed the disastrous World War I and was labeled a draft dodger, just like his grandson Donald during Vietnam, and would be expelled and barred from returning to his own country.

Friedrich Trump passed away from pneumonia at the end of WWI in the U.S., where he was welcomed back as a German immigrant. He left some real estate behind, which his son Fred Trump would turn into billions that Donald inherited and has struggled to manage after various failures and bankruptcies.