Why did Americans build fortunes in the oil and steel industries?

Americans built fortunes in the oil and steel industries due to the rapid industrialization and urbanization of the late 19th and early 20th centuries. The demand for oil as a fuel source and for emerging technologies, such as automobiles and machinery, drove significant investments and innovation in the oil sector. Similarly, the growth of infrastructure and construction created a booming market for steel, essential for railroads, buildings, and bridges. These industries were characterized by high profit margins and monopolistic practices, allowing industrialists like John D. Rockefeller and Andrew Carnegie to amass vast wealth.