What was the Dawes Severalty Act of 1887?

The Dawes Severalty Act of 1887, which is also known as the General Allotment Act, gave the President of the United States the power to evaluate American Indian tribal land in order to divvy it up and dole out allotment to individual Indians, with the caveat being that those who agreed to live separately from their tribe on these allotments would be given United States citizenship.
The Act was a signed into law by President Cleveland and aimed to accomplish the following six goals:
To break up the social units of tribes
To encourage the initiative of individuals
To aid in the progress of native farmers
To reduce administrative costs of natives
To secure portions of the reservations as Indian land
To free up the remaining land to be settled by white people for profit
The provisions of the Act stated the following:
Individuals under the age of eighteen would receive 40 acres each, individuals over the age of eighteen would receive 80 acres each, and the head of a family would receive 160 acres.
The above allotments are held in trust for 25 years by the US Government.
Individuals could select their land within a period of four years; if they did not select it, the selection would by made on their behalf by the Secretary of the Interior.
The Act had a largely negative impact on the American Indian people, with the land they owned being dramatically decreased in the name of white greed.