It really depends on the period and location, but it was generally uncommon. Crime in Alaska and the Yukon during the gold rush period (1880-1917) was linked to three factors: transient population, the presence of law enforcement, and easy transportation into and out of the area. The book I'd recommend most is William Hunt's Distant Justice: Policing the Alaskan Frontier. It was published in 1987, but it's still a very good work on the history of crime and punishment in Alaska during the gold rushes. I also highly recommend Terrence Cole's definitive, annotated version of James Wickersham's memoir Old Yukon: Tales, Trails and Trials. Wickersham was one of Alaska's top judges during the gold rush period, and he had a lot to say.

Now, let's go into the three factors. Crime was most common in areas with a transient population. In settled areas during the gold rush period, the population was never so great as to give a thief cover. Crime was highest in port cities and boomtowns where people didn't know each other, were constantly coming and going, and community institutions were not present or not strong enough to deter crime. This meant places like Juneau, Skagway, Nome, Circle, and Fairbanks ─ among other gold rush cities ─ had surges of crime during their heyday.

The second factor is easy transportation into and out of an area. While crime might surge in Nome, Fairbanks or Circle during the summer, it made no sense for a criminal to work during the winter, when escape was impossible or supremely difficult. Once the ocean off Nome froze, or the rivers of the Interior solidified, crime tended to drop. It simply made no sense to commit crimes without a getaway plan or a secure position (through corruption or influence) that meant retaliation was impossible. In Skagway and Juneau, where the ocean did not freeze, crime was a problem year-round.

Note that this doesn't preclude crime in isolated areas, it merely discourages it. Between September 1899 and October 1900, when Nome dropped to 4,000 to 6,000 people, there were six murders in Nome, and street gunfights were rare. Nevertheless, the Nome Chronicle published an editorial during this period stating, "While all the officials talk, the burglar and footpad ply their vocations and honest pedestrians mush home with their hands on large sized guns they carry in outside pockets ... Nothing is done to discourage crime."

The third factor is the presence of law enforcement. Read almost any memoir or history of the Klondike Gold Rush, and you'll hear praises (and rightfully so) for the Northwest Mounted Police. The Mounties, under the command of Charles Constantine and (after 1898) Sam Steele, securely patrolled the Yukon. Note that they did not prevent all crime ─ small scale grift, gambling and prostitution still happened ─ but they did enough to prevent the outright violence present in Skagway, Circle and American cities where law enforcement was nonexistent. In Juneau, which had the first (wholly) Alaskan gold rush, the establishment of large, industrial-scale gold mines brought infrastructure and an organized police force in place by the time the Klondike rush began. Thus, while it had its freewheeling period of crime, Juneau had settled down by the time the Klondike burst onto the scene in 1896.

Even in places without organized law enforcement, miners courts conducted justice. One step above a mob, these courts could be found in mining camps across the West throughout the 19th century. In the event of a crime, a prospective criminal would be seized, a jury and judge empaneled, defense and prosecution attorneys appointed, and the whole thing done as an impromptu trial. Justice was swift, uneven, and likely violent. In 1888, two Native men were lynched in Juneau after being sentenced by a miners' court.

Hunt shares a more typical account on page 58 of his book. In 1897, three Californians traveling the Chilkoot Trail found their cache (it often took multiple trips up and down the trail to bring up supplies ─ it's a tough hike; trust me on this one) raided by thieves. Two men were caught with some of their items. A miners' court was convened and sentenced them quickly. One of the men ran away and ─ rather than face the court's sentence ─ shot himself in the head. The surviving thief was sentenced to 50 lashes with a knotted rope and was ordered to parade into Dyea with a placard labeled "THIEF".

Large gold thefts were uncommon. Everyone understood the value of gold, and so it was guarded well, when it was present in large quantities. Far more common were simple holdups or robberies for an individual miner's "poke" earned in exchange for a day's labor on an established mine. Even more common were gambling scams or simply getting a miner so drunk as to rob him blind.

One of the most spectacular gold thefts was aboard the steamboat Tanana in 1906. In that year, "Bobby" Miller took a job as watchman aboard the steamer. During the course of his job, he stashed lead shot aboard the boat while it was moored in Fairbanks. He knew it would soon leave to head downriver with millions of dollars of gold aboard. Once the Tanana left, he managed to get one of the gold boxes into his stateroom and swap 38 gold bricks with lead birdshot, then re-seal the armored box.

Unfortunately for Miller, some other thieves struck the steamship Ida May, which was to carry the gold from the Yukon River to San Francisco. During the course of this second theft, Miller's act was discovered. He had taken some $79,000 worth of gold, stashing $50,000 in one place during the Tanana's voyage south, and $29,000 in another place. While he led police and prosecutors to the $50,000 stash, it is believed that he kept some or all of the $29,000 stash. We believe this because according to Seattle newspaper accounts, one of Miller's partners was arrested with some $10,000 in cash in 1908, and Miller lived an auspiciously high life afterward.

In 1907, two men thought they had learned their lesson from Miller's experience and came up with an alternative. Frederick Wright and R.P. Quinn got jobs aboard the steamer Seattle No. 3 and proceeded to steal 83 ounces of gold worth $15,000. Rather than risk carrying it themselves, they decided to chuck the gold overboard in a sack with a float attached to mark the spot.

It didn't go as planned. The rope broke, and the sack sank to the bottom of the river, lost forever. Wright and Quinn were charged and sentenced with theft, but they never got to enjoy it.

Trail thefts and holdups were spectacularly uncommon, but they were known to happen and were all the more notable for their rarity. In 1905, Charles Hendrickson ─ called the "Blue Parka Bandit" in contemporary accounts ─ escaped from the Fairbanks jail (a log cabin in the two-year-old town) after a series of trail holdups and horse thefts. He and another man (who had stabbed a guard during his escape) were recaptured and sentenced again, escaped and recaptured, escaped and recaptured, escaped and recaptured. And no, those repetitions are not a mistake.

That isn't to say Alaska didn't have some spectacular thefts. On Dec. 30, 1922, a 40-year-old prostitute named Nellie Bates collaborated with a roadhouse proprietor named William Schermeyer to steal $30,000 from a dog sled mail delivery bound for McGrath. They actually got away with it, too, and the crime was only discovered years later, after Schermeyer ─ having been swindled by a series of women in Oregon and California ─ confessed to the theft. Bates was acquitted by an Alaska jury captivated by her story.