The expansion of the rail networks led to
a. a growth in the steel industry.
b. a growth in the textile industry.
c. a decline in the coal industry.
d. a decline in the meatpacking industry

The correct answer is A:a growth in the steel industry. In order to build the railroad network, large amounts of steel were needed for the rails on the tracks. Steel was also a key component of the locomotives themselves. Thus, the expansion of this system required more steel to be produced and a growth of this industry.