How did the economic impact of the homestead act contribute to the close of the frontier in the late 19th century

Signed into law in May 1862, the Homestead Act opened up settlement in the western United States, allowing any American, including freed slaves, to put in a claim for up to 160 free acres of federal land. By the end of the Civil War, 15,000 homestead claims had been established, and more followed in the postwar years

c or d both can be the answer