The answer is Farmers
As the Railroads in the early United States moved west wards towards the Pacific Coast, it was still going to operate in a region with a very thin population.
The Western parts of the country were considered poor and not many people had moved there except for farmers and miners.
However, once the railroads started to move west wards, many farmers looked at it as an opportunity to make a quick buck. They were willing to sell the best agriculture land in return for high profits.
Farmers also believed that by selling good land and providing easy routes to railroads might mean greater settlement in the region, which would directly lead to more business for them.
The transcontinental railroads were crucial in the union and success of the United States in these early years.
