what factor helped to promote america's huge industrial growth during the period 1860-1900?

Answer 1

Maybe more than any one thing the railroads. I myself would also highlight the development of the modern corporation and an extraordinary commitment to engineering and applied science education via the land grant colleges.

Answer 2

assembly lines, steam engines, the influx of immigrants
you can always google the history of the industrial revolution, but when you look at the abundance of resources, you can see that it was obvious that we had to become a self-sustaining country.