Final answer:
The Western states and territories experienced the greatest increase in railroads and significant economic growth between 1870 and 1890.
Step-by-step explanation:
The area with the greatest increase in railroads and significant economic growth between 1870 and 1890 was the Western states and territories.
During this time, the Western states and territories experienced a massive expansion of railroad mileage, which fueled economic growth. The construction of railroads opened up the region for trade, transportation of goods, and settlement, attracting businesses and investors. As a result, industries flourished, cities grew, and the Western states and territories became important economic powerhouses.
For example, the completion of the First Transcontinental Railroad in 1869 connected the East Coast to the West Coast, providing a direct route for trade and transportation. This led to the development of industries such as mining, agriculture, and manufacturing in the Western states and territories, contributing to their significant economic growth.
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