I assume that this question has to do with the United States. I will address the boom in industrialization after the Civil War, not the early moves towards industrialization in the first half of the 1800s. Three of the most important factors that contributed to industrialization were:
- Technological innovation. Perhaps the most important such innovation was the invention of the Bessemer process, which allowed steel to be made quicker and at lower cost. This made industrialization possible because steel is an important part of machinery, factories, and many products. Other technological advances, like the invention of the telegraph and the electric light also helped with industrialization.
- Westward expansion. This contributed to industrialization in two main ways. First, it gave access to new resources in the areas that were being “opened.” This gave industry more resources to work with. Second, it necessitated the creation of railroads, which increased the demand for industrial goods like steel and railroad cars. This increased the need for industry.
- Immigration. Immigration to the United States allowed the US to have a large supply of cheap labor. This made industrialization possible because early industries tend to rely heavily on unskilled labor.
These are, in my view, the most important factors that allowed a boom in industrialization to happen in the US after the Civil War.