Question

In the 1840s the main argument and Congress over the transcontinental railroad concerned

Answer 1

In the 1840s the main argument and Congress over the transcontinental railroad concerned the impact it would have on individual towns, since the railroad caused a major disturbance in many of the towns it passed through. 

Answer 2

In the 1840s the main argument and Congress over the transcontinental railroad concerned the way it could impact individual  small towns and villages. The problem was that the railroad created many problems and unnecessary noise and rush in many of the towns it passed through.