In 1890, the superintendent of the U.S. Census announced that the American West had been settled to the point that there no long was a frontier line in the United States. This came to be known as the closing of the frontier. How did the Transcontinental Railroad and Homestead Act contribute to this?
A.
by enabling the settlement and annexation of Texas
B.
by allowing settlement of California during the Gold Rush
C.
by making it easier for Americans to settle in the West
D.
by helping Americans settle in Mexico and Canada