The correct answer to this open question is the following.
One reason for American imperialism was because of economic needs. Farming and factory production in the United States in the late 1800s had some issues. In the cases of Farmers, they were upset because railroads charged too much money to transport their goods to other parts of the country. Farmers alleged that there was no competition in the railroad industry and that is why railroads charge what they wanted to ship products. This pressure made the federal government pass legislation such as the Commerce Act of 1887.
Regarding industry, the American manufacturing plants made workers work for long hours under dangerous and unhealthy conditions. The salaries were not good. Companies owners got richer because of these factors.