What problem did Manifest Destiny create?

Manifest Destiny created the central problem of conflict with Native American nations who already lived on the lands the United States sought to occupy, producing forced removal, broken treaties, wars, and the eventual dispossession of dozens of tribes from their homelands. The conflict began long before the 1840s but accelerated as American settlement crossed the Mississippi. By 1800 the United States had already taken vast tracts from Native nations through treaties signed under duress, military pressure, and outright fraud, especially east of the Mississippi after the Treaty of Greenville in 1795 ended the Northwest Indian War.

President Thomas Jefferson favored gradual assimilation but already in 1803 wrote of pressing Native nations into trading their lands for goods until they were too dependent to resist removal. President Andrew Jackson made forced removal explicit federal policy. He signed the Indian Removal Act of May 28, 1830, which authorized the President to negotiate removal treaties with eastern tribes and offered them lands west of the Mississippi in exchange for their ancestral territories.

Among the so-called Five Civilized Tribes (Cherokee, Creek, Chickasaw, Choctaw, and Seminole), each suffered a devastating relocation. The Choctaw moved between 1831 and 1833, losing perhaps 2,500 of about 17,000 along the way. The Creek were forcibly removed in 1836 to 1837 with about 3,500 deaths. The Chickasaw moved between 1837 and 1838 with a smaller proportional toll because they had more time to organize. The Seminoles fought three wars to resist removal and were never fully relocated; the Second Seminole War from 1835 to 1842 was the longest and bloodiest of the Indian wars. The Cherokee were removed in 1838 to 1839 along the route now called the Trail of Tears, despite winning their case Worcester v. Georgia (1832) before Chief Justice John Marshall's Supreme Court; about 4,000 of 16,000 Cherokee died.

Plains and Western tribes faced their own conflicts as Manifest Destiny extended American settlement. The Sioux Wars from 1854 to 1890, the Apache Wars from 1849 to 1886, the Modoc War of 1872 to 1873, the Nez Perce War of 1877, and many others culminated in the massacre at Wounded Knee on December 29, 1890. The Dawes Act of 1887 attempted to break up reservation land into individual allotments, transferring perhaps 90 million acres from tribal to non-Native ownership by 1934.

By 1900 most surviving Native peoples had been confined to reservations, often far from their homelands, with their populations reduced by warfare, disease, starvation, and despair to perhaps a quarter of their pre-contact totals. The Indian Citizenship Act of June 2, 1924 finally granted U.S. citizenship to all Native Americans born within the country.