What was the largest industry by the late 1800s

By the late 1800s German chemical and electrical industries set the standard worldwide.

Explanation:

Germany's spectacular growth was due in part to ample iron and coal resources.

Library of Congress

Old industries expanded and many new ones, including petroleum refining, steel manufacturing, and electrical power, emerged. Railroads expanded significantly, bringing even remote parts of the country into a national market economy. Industrial growth transformed American society.