Allotment
Allotment, formally, refers to the the practice of granting small plots of land to individual members of federally recognized tribes by the U.S. Government. The practice traces its origins to the late 18th century, when the United States began to establish formal governments and treaties as an independent nation.

British colonial forces were interested in establishing strong mercantile forces to counter the other rising colonial powers such as Spain and France, and together these groups seized vast swathes of land from the indigenous peoples of the area with little consideration of their views on land ownership and usage. After U.S. independence, the goals of European settlers changed from that of being British colonial citizens to an American existence, which was to co-exist with Native existence for the next thirty years or so.

White American attitudes towards Native Americans took a much more violent position after Andrew Jackson’s election in 1828. His policies of Indian Removal caused widespread destruction of people, culture, history, and knowledge, exemplified most infamously in the Trail of Tears. By the mid-19th century more and more new European immigrants were settling on the edges of native lands and causing extensive conflicts; as a response, reservations for uprooted natives were made, as well as causing the widespread support from White Americans of assimilating Native Americans.

American settlers have long recognized the threat of Indians to their claims of the right to occupy the lands of North America, and the existence of any sort of Indian Mentality poses a threat to the legitimacy of the American settler state. With wholesale slaughter losing popularity as a form of dealing with the Indian problem, assimilation became the preferred tactic to remove traces of indigeneity from the public eye.

Under the new assimilation policy, the U.S. Senate passed a law that would later be recognized as influential in restructuring Native livelihoods, the Dawes Act. The Dawes Act, also known as the General Allotment Act of 1887, served as part of the assimilation policy through dismantling communal ownership of land and redistributing it into private property of individuals subject to state inheritance laws. The direct provision of the act was stated to be that, depending on age and marital status, a Native individual/household would receive between 40 and 160 acres of land, and that all of it is held in trust by the U.S. government; all unclaimed land, otherwise, was free for the U.S. to do as they pleased. Between 1887 and 1934, 90 million acres of Indian lands was lost due to allotment. Most states dictate that, in lieu of a will, inherited land should be evenly divided among heirs. Since most American Indians do not make wills, land holdings tend to get split into smaller and smaller pieces in each generation and subsequently become worthless as usable land. (See fractionation.)

Allotment as an assimilation tactic has been wildly successful for the American settler state in many ways. The most obvious of these is that the state made a smooth transition from the illegal, unjustifiable seizure of land, to seizures done from the word of law that all Natives had to adhere to. From the Dawes Act and its extensions the Curtis Act and the Burke Act, the following list of objectives were set as the endgame for allotment:

Breaking up of tribes as a social unit. The tribal structure, feared by White Americans, could now be broken down into approachable, nuclear, and patriarchal familial structures. The policy of granting 160 acres to the head of household is a good example of how small differences lead to big effects - for example, women in many different tribes were tasked with being caretakers for the land. By removing that aspect of social stability, gender roles everywhere were uprooted; men worked in traditionally feminine roles and had their standing reduced under European masculinity standards, and women became dependent on their husbands.

Encouraging individual initiatives. Caring for small, individual plots were thought to help encourage Natives to produce more, to think of the self more, and to profit more like their white counterparts. Making individual success stories of the assimilated Native, and how they succeed against all odds, were going to be useful in justifying the continued acts of violence against Native communities.

Furthering the progress of native farmers. Having native farmers adopt western farming tactics were borne of a desire to civilize the savage and to introduce them to a lifestyle they never imagined they could have, for better or for worse. This ignores the fact that replacing polyculture with monoculture is destructive to local biodiversity, and ignores how Native farmers have systems of knowledge about the land they’ve been cultivating for centuries.

Reducing the cost of native administration.

Opening the remainder of the land to white settlers for profit.

An effect of having lots of land divided into small portions is how susceptible it is to exploitation; the Burke Act was instrumental in coercing many Natives to sell what little land they had for subpar rates to white buyers.

Further reading:

Debo, Angie. And Still the Waters Run: The Betrayal of the Five Civilized Tribes (1940)
Frantz, Klaus. Indian Reservations in the United States (1999)
Grande, Sandy. Red Pedagogy (2004)