The Dawes Act (1887) was passed to hasten the Americanization of Indians. Under the provision of the act:

• Native American tribes were officially abolished.

• Each male American Indian was allotted 160 acres of reservation land as his own private property. Private property was expected to replace tribal land ownership, as each Native American became a farmer.

• Those who adopted this way of life were given United States citizenship and the right to vote. In the 1924, all Native American were made citizens.

Source: http://www.ourdocuments.gov/doc.php?flash=old&doc=50#

http://www.archives.gov/education/lessons/fed-indian-policy/