Alternatively, how many people did it carry from east to west?
How was it all decided? Were there competing bids from different companies? Did the government get priority because of deals with the railroad companies?
Re: goods, one thing that caught my eye (and stuck in my memory) was the effect on oyster production.
As oysters are capable of enduring low tides and the like they will survive for several weeks if kept damp and cool. In addition to transporting seed oysters to the West Coast the transcontinental railroad allowed major markets in Detroit, Chicago, St. Louis, and so forth (source, p 14).