The map shows railroads of the North and South in 1850 and 1861.

A map showing the railroads of the North and South in 1850 and 1861 in the U S.
Which of these was NOT an effect of the growth of the railroad system?

Trade increased between the North and the South.
Western railway hubs became the center of the system.
The South remained tied to agriculture.
Cities and towns with railways grew in population and wealth.