In the late 1800s the growth of the railroad led to mid western cities like minneapolis and cleveland becoming agricultural centers unsettled territories industrial centers lumber centers

Industrial centers is your best answer.

As cities like M & C are in towards the middle of the country, they tend to be the one of the stopping points for travelers going both directions. This can lead too a large increase in population, wares and shipments & goods, as well as money flowing through, which can lead to the expansion of the cities infrastructures & development needed for a city to grow.

~

c. have a great day ~ma.tiah