In the 1870s and 1880s, the US economy grew faster than ever before and quickly became the largest economy in the world. What factor(s) contributed to this incredible economic growth the most? Some...

In the 1870s and 1880s, the US economy grew faster than ever before and quickly became the largest economy in the world. What factor(s) contributed to this incredible economic growth the most? Some possible factors you can mention are big business owners, known as robber barons, immigration, the engineering revolution, railroads, etc.