telegraph transcontinental railroads American Old West American Civil War railways purchase of Alaska Russia overthrew Hawaiian monarchy Republic of Hawaii annexed Puerto Rico Guam Philippines Treaty of Paris (1898) Spanish–American War Foraker Act Insular Cases American entry into World War I Jones–Shafroth Act American Samoa Second Samoan Civil War U.S. Virgin Islands Denmark settlers Spain Native Americans
National infrastructure, including telegraph and transcontinental railroads, spurred economic growth and greater settlement and development of the American Old West. After the end of the American Civil War in 1865, new transcontinental railways made relocation easier for settlers, expanded internal trade, and increased conflicts with Native Americans. Mainland expansion also included the purchase of Alaska from Russia in 1867. In 1893, pro-American elements in Hawaii overthrew the Hawaiian monarchy and formed the Republic of Hawaii, which the U.S. annexed in 1898. Puerto Rico, Guam, and the Philippines were ceded by Spain in the same year, by the Treaty of Paris (1898) following the Spanish–American War. Puerto Ricans did not gain citizenship either through the Foraker Act (1900) or the Insular Cases (1901), but only one month prior to American entry into World War I though the Jones–Shafroth Act  in 1917. American Samoa was acquired by the United States in 1900 after the end of the Second Samoan Civil War. The U.S. Virgin Islands were purchased from Denmark in 1917.
