The main factor that contributed to the rise of the labor movement in the United States in the 1800s was the rise of industrialization. As the US economy became industrialized, the conditions that were necessary for the formation of labor unions arose.
During the 1800s, and particularly after the Civil War, the United States became more and more industrialized. This meant that more of the country’s work was being done in factories. When a country industrializes, it changes in many ways. These changes helped to make the labor union possible.
First, industrialization tends to make workers less happy. Before industrialization, workers typically worked as their own bosses and at their own pace. They might have had to work very hard at times, but they could decide when and how hard they would work. Even those workers who worked for other people worked in relatively humane conditions. They typically worked as assistants to their bosses, as with the apprentices who would work with their boss as they learned their trade. With industrialization, this ends. Industrial workers have very little control over their work lives. They are told when, how, and how fast to work. They do not get to work along with their bosses and feel equal to them. They are typically forced to work as fast as possible so that their factory can be as productive and profitable as possible. Workers who have to work in these conditions tend to become unhappy with their jobs. This can lead them to form unions to try to better their working conditions.
Second, industrialization puts many workers together in one place. It creates huge factories with many workers. Those factories exist near to other factories in large cities. This means that many workers are being put together in one place. Because of their numbers and their proximity to one another, it is relatively easy for them to discuss issues that affect them. Since industrialization put so many workers so near to one another, it gave them the opportunity to meet and to form unions.
In essence, industrialization gave workers the motive and the opportunity to create unions. It brought about working conditions that made workers feel exploited. It created large cities that gave them the opportunity to meet with other workers and organize. In these ways, it was the main factor that contributed to the rise of the labor movement in the United States.
(If you need more factors, you could also argue that immigration helped to bring about unionization. You could say that many of the immigrants who came over in the late 1800s held leftist beliefs that were supportive of the ideas of unions. If you make this argument, however, you should be careful. The union movement started before the really massive wave of immigration late in the century. In addition, you could argue that the immigrants hurt the labor movement by allowing many Americans to oppose unions on nativist grounds. However, this is another factor that you could mention if you feel it is necessary.)
Industrialization was the main factor for the labor movement in the 19c. This is because industrialization changed the way commodities were produced. Instead of individual families providing all necessary products for themselves, people started to enter trades. Trades are specific jobs done by a group of people. The products made from trade jobs are then sold. This allowed for people to specialize which was a huge part ofthe labor movement