The north's control of railroads gave it advantage during the civil war because it could

The Union had about 2/3 or more of the national railroads during the Civil War. Later, that figure was much higher as Union raiders systematically destroyed the rails in the south. Also worthy of note is that the railroads of the south were of differing gages so that a train could not transfer from one line to the next. Long-distance shipment of war materials was very difficult. The nothern railroads were nearly all standard gage (4 feet 8.5 inches) so that a train could be routed from one company's tracks to another with relative ease.