From the textile factories in Lowell, Mass., where the first labor unions were formed, to the railroad strikes in the Southwest led by the Knights of Labor, which thrust unions and their demands into the national spotlight there have been many triumphant moments in labor movement history. But not every moment was so joyous. Indeed, it's a tragedy that we have to thank, in part, for many of the standards and workers' rights we now enjoy. The Triangle Shirtwaist fire in 1911 started as a small factory fire, but quickly became the deadliest industrial accident in New York City history due to insufficient fire escapes and factory bosses giving little care to fire and safety measures. In the aftermath, a commission was formed to investigate the cause of the 146 deaths, and within a few years, legislation was introduced to create and enforce stricter workplace-safety laws, safer factories and shorter hours. But the movement didn't stop there. The tragedy boosted the strength of the burgeoning union movement and went on to inform many of the rights we enjoy today, including minimum wage and collective-bargaining rights.