The son of Scottish immigrants, McDonald was born in Antigonish, Nova Scotia.[3] He was an unsuccessful prospector, having tried his luck in the Colorado gold fields, before heading to the gold rush in Juneau, Alaska, in the late 1880s.[4] In 1895[1] or 1896,[4] he was in the Yukon, employed by the Alaska Commercial Company at Forty-Mile to buy mining properties.[5] Gold was discovered in the region in 1897.
He was nicknamed the "Big Moose from Antigonish", "Big Alex" and "Big Mac".[2][6] He was described by a contemporary as:
... a large brawny, swarthy man, canny and close of mouth, with a curious habit of slowly rubbing his chin whenever a new proposition is presented to him. He makes it a rule to first say "No" to every proposal, however alluring, thus gaining time to think it over.[5]
One of the early arrivals in the Klondike, he purchased either half[1][7] or all[2][4] of Claim 30 on Eldorado Creek from a Russian named Zarnosky or Zarnowsky for a sack of flour and a side of bacon. That claim proved to be one of the richest of the Klondike,[4] yielding $5000 a day.[2] McDonald's slowness of speech hid a shrewdness and business acumen that enabled him to amass a tremendous fortune, somewhere between seven and 27 million dollars.[1] Rather than just work that single piece of land, he leased it to two other miners, who did the actual work for half of the proceeds.[4][8] In the first 45 days, that amounted to $30,000.[8] He then proceeded to buy up other claims, and by the end of the year he had acquired 28.[1] By 1898, he had interests in 75 mines,[1] making him the largest landowner and employer in the area.[4]
That year, when the local Catholic church burned down, he donated $30,000, more than enough to pay for its rebuilding.[1][4] When Father William Judge started building St. Mary's Hospital, McDonald once again made a large donation. In the winter of 1898–1899, he toured Europe,[9] finding time to marry, in London, Margaret Chisholm, the twenty-year-old daughter of the superintendent of the Thames Water Police, and to be received by Pope Leo XIII, who made him a Knight of the Order of St. Gregory in appreciation of his generosity.[4][10]
However, though the gold rush eventually died down, McDonald continued to buy land claims, now mostly worthless, squandering his money. Living alone in a cabin on Clearwater Creek, he died of a heart attack in 1909.[1] His remaining assets of $30,000 did not cover his debts.[1] His widow benefited from a life insurance policy urged upon him by another Klondike tycoon, Belinda Mulrooney.[11]
McDonald's legend was retold in an anonymous poem called "King of the Klondike" (c. 1910).[6]
His resting place is in the cemetery in Dawson City.[1]
