How did America’s economy, industries, and population grow after the Civil War? three examples with explanation

United States was marked by tremendous expansion of industry and agriculture as well as the spread of settlement across the continent. The population of the United States more than doubled during this period. In its report on the 1890 census the Bureau of the Census declared the frontier closed. Most of the economic growth was concentrated in the Northeast, Midwest, and plains states. The South remained largely agricultural, its total industrial production totaling about half that of New York State. The Northeast  clearly emerged as the industrial core of the nation with 85 percent of the nation's manufacturing, processing raw materials from the Midwest and West.

i think it is the byzantine empire