I just noticed a Salt Lake Tribune article about a fascinating episode of labor terrorism in Utah history by Utah historian and Times and Seasons blogger Ardis Parshall. (ht: T&S sidebar)
During the construction of the Hotel Utah in 1910, a bomb demolished the iron frame that had been erected:
A few minutes past 3 a.m., a terrific explosion, fueled by dynamite and nitroglycerin, erupted from the northeast corner of the construction site. The concussion knocked one of the watchmen to the ground, twisted part of the hotel’s iron framework beyond repair, and shattered windows in the office buildings across South Temple. In the words of one witness, there was “not enough glass left to make a pair of spectacles.” Downtown residents covered in dust and shards of glass ran into the street, some convinced that the comet had actually struck Salt Lake City.
Although office buildings across South Temple were damaged, the Temple across Main Street luckily remained undamaged except for displacement of the Angel Moroni’s horn.
It turns out that the bomb — together with another that detonated the previous December — was an act of terrorism perpetrated right in Salt Lake City by supporters of a national workers’ union:
Investigation began before daylight, with suspicion instantly falling on the ironworkers’ union, which had objected to the open-shop policy of the hotel’s contractor. The union also was suspected the previous December when a similar bomb exploded in the hotel’s foundation, but no solid evidence was found to link either crime to any culprit. . . .
More than two years later, the Hotel Utah bombings were solved when three men – including McNamara, the union man who had offered a $500 reward – confessed to having set both bombs, along with dozens more around the country, one of which had killed 21 men working at the Los Angeles Times.
In these days when headlines of terrorist bombs dominate the daily news, who would have thought that Salt Lake City was dealing with labor terrorists using similar techniques nearly 100 years ago?
ABEV: a bird's eye view 
It is events like this that are an important contextualization of some of the early Church statements on labor unions. Ardis is wonderful and thank you for highlighting the story.
Exactly.
Thanks, John, for caring enough to give this story a little more life. If the Trib let me write weekly instead of monthly so that I could do two-parters, I would have done one article on the repair of the statue, and another on the union angle. I love it whenever I find a connection between Mormon/Utah history and something going on in the wider world. The whole episode of the ironworkers’ bombings of 1908-1911, all across the nation, resulted in Samuel Gompers’ testimony before Congress (it was his AFL to which the ironworkers’ union belonged). Clarence Darrow defended the bombers during the LA Times phase of the trials. In other words, it was a big, big story, and you know that church leaders were following it if for no other reason than it had involved Salt Lake at one point.
[…] union terrorists bomb the Hotel Utah (now the Joseph Smith Building) in 1910. And Utah remains a Right to Work […]
To be honest, I was not aware of these events in Utah’s history. The most surprising part of the story is that the bombings were so closely tied to a worker’s union – something you’d expect to be run ethically and responsibly.
Great story and thanks for sharing.