Why the railroad land grant are has a checkpoint pattern. Explain this idea in a short essay

The expectation was the railroads would quickly sell the land to settlers to raise the money to pay for the building of the railroad. However, in practice government conditions usually prevented, and railroads often chose not to sell the land. Instead, railroads usually used their land grants as collateral to obtain loans.

On each side of the tracks, but to help meet expenses, ten was changed to twenty miles on each side in 1864. Because of the checkerboard pattern twenty miles would result in ten railroad blocks on each side of the tracks, and the federal government would keep most of the non-railroad blocks of land.

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