How did the federal government encourage and facilitate the construction of thousands of miles of railroad tracks throughout the west

It is known that the American westward movement has occurred with settlements of intermittent flurries. Pioneers or the settlers of the west as they are called usually migrated together with or as families and settled in the rivers of the West. However, due to the rivalry between the West and the East, both have not tried migrating into the same place.

During the 19th century, the federal government encouraged the western expansion by land grants. The settlers were granted with a 160-acre land in the west given that this land can be farmed for six months. Other than that, this land can also be bought by a dollar and 25 cents per acre. It was quite unconventional for the few farmers to go with the latter option, but still, many land speculators did. Because of this, there are thousands of acres of homestead land that were purchased by speculators. 

where is the section with the question?

answer; andrew jackson approved nullification by signing it into law,and john calhoun opposed it saying it was unconstitutional;