Answer :
The main reason was the construction of railroads.
Two railroads especially were important in making Chicago the steel-making and manufacturing center and those were Galena & Chicago Union Railroad. Chicago was a small town that boomed. Their boom started as there were factories in Chicago that manufactured rails for many railroads among other things.
Two railroads especially were important in making Chicago the steel-making and manufacturing center and those were Galena & Chicago Union Railroad. Chicago was a small town that boomed. Their boom started as there were factories in Chicago that manufactured rails for many railroads among other things.