If a Native American in the early 1800s decided they wanted to leave tribal life behind and voluntarily join the United States, would they of been able to? How would life of been and what rights would they of been afforded? Obviously I'm sure they would be heavily prejudiced against, but would they legally been a US citizen?
##Part 1
Yes! No! Maybe so!
This isn't such a straightforward question as one might initially think. First, some ground rules for context (because context is everything).
First, there are many, many different Tribes across what is now the United States. In the early 1800s, treaties were formed between Tribes and the United States. These treaties were sometimes made with individual Tribes and sometimes with groups of Tribes. Many of these treaties are similar, but many of them have terms and stipulations specific to that Tribe or Tribes.
Second, the "early" 1800s is a bit too broad. If we look at this early period as being 1800 to 1830, these 30 years saw many developments and changes in the political landscape and power dynamic between Tribes and the United States. For example, the Doctrine of Discovery--the concept that lands "discovered" by European powers belong to said powers and absolve Indigenous Peoples of their title to the lands they occupy because they're pagans--was articulated into the American legal system in 1823 in the conclusion of the Supreme Court case Johnson v. McIntosh. This case is one of the foundational cases that defines American federal Indian policy and completely changed how Tribes were viewed and interacted with prior to 1823.
With the context established, let's continue building the picture we see here with a framework of how to understand citizenship and Indians. My comment here will speak from a very generalized approach regarding how the notion of citizenship applied to Indians was conceptually and legalistically developed. There are always exceptions to be made.
##Indians in the Constitution
The U.S. Constitution set the bar for how Indian Tribes were accounted for in the American political and legal worldview. There are applications to be made from both explicit and implicit clauses in the Constitution, but are few in number, leaving a broad base from which federal Indian policy gradually developed. The major clause dealing with Indians is Section 8, paragraph 3 that gives Congress the power to "regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes." Considering that Indian Tribes retain inherent sovereignty and have existed as polities long before the United States entered into the picture, this clause was written according to the circumstances the United States faced at the time: Tribes were, and are, nations. As such, much of the Constitution did not deal with Indians as if we were citizens or make stipulations for us to become citizens for a very long time. Indeed, there was practically no change in this from 1787 through most of the 1800s with how the Constitution specifically was interpreted to define the relationship between Indians and the United States.^1
As the power dynamic would shift with Manifest Destiny and genocidal policies, Tribes became increasingly subjugated, falling further and further under the purview of the United States. As described here, efforts to assimilate American Indians intensified as settlers began expanding westward. This created a situation in where the United States could begin precluding Tribes from exercising sovereignty by incorporating us into American society. To properly justify this, the Doctrine of Plenary Power had to be created--through the courts.
##Indian Land, the Supreme Court, and Legislation
In 1903, the Supreme Court case of Lone Wolf v. Hitchcock drastically altered the historic precedent of how the United States interpreted its capability of exerting power over Indian lands and, subsequently, Indians.
Indians, under the doctrine of discovery, had clear equitable title to the lands they occupied, and until they voluntarily chose to sell all or a part of their lands, it was the responsibility and duty of the United States to protect them in the undisturbed enjoyment of their territory. However, in Lone Wolf v. Hitchcock, the Supreme Court ruled that the federal government, in the exercise of congressional powers, had, and had always had, plenary powers over Indian lands and property. Plenary power was implied through the application of convoluted judicial logic in defiance of the historical record and specific articles of a treaty written and explained by federal representatives ... Once it is implied that this power also involves the ability of the federal government by itself to force a purchase of the lands, there is no way the implied power can be limited. If the government can force the disposal of lands, why can it not determine how the lands are to be used? And if it can determine how the lands are to be used, why can it not tell the Indians how to live? And if it can tell the Indians how to live, why can it not tell them how to behave and what to believe?^2
While a certain amount of implied powers were narrowly exercised with regards to regulating the relationship with Tribes as interpreted from the clauses in the Constitution, Lone Wolf v. Hitchcock articulated a very broad and very dangerous doctrine that heavily limited the ability of Tribes to exercise sovereignty and further entrenched us as subject to the United States. Plenary power resulted in an expansion of implied power over Tribes, chief among them being the naturalization of citizens from Indian Tribes.
This case, however, expressly identified a key connection: that of an Indian to land. Reservations, Indian Territory, trust lands... Indians have been historically defined by our connection to the lands we occupied. Treaties made with Tribes often reserved a land base from which a Tribe may operate, setting up defined boundaries where it can be stated that the jurisdiction of one polity ends and another begins. As such, the degree to which the United States exercised authority over Indians was often shaped by the circumstances around the land in which this authority was recognized.
By 1880, it was determined that Indians did not qualify under the Fourteenth Amendment as we continued to dwell in communities (with land) that were not politically aligned with those considered to be people of the United States (fun fact: Indians were not considered "persons" under American law until 1879--thanks, Standing Bear!). It was in 1884 with the case Elk v. Wilkins that the applicability of the Fourteenth amendment was tested again, but on an individual level. Remember how I said that the relationship of Indians has always been defined by our connection to land? Yeah...
...it was to be anticipated that in the case of John Elk--who had left the jurisdiction of his tribe, moved to Omaha, Nebraska, purchased a home, become [sic] a member of the state militia, and paid taxes--that the recognition of his American citizenship would most likely follow ... The Supreme Court, however, followed previous court rulings and adopted the interpretation of [an] earlier Senate Judiciary Committee report ... the majority in Elk insisted that absent a specific naturalization law, naturalization provision in a treaty, or action in a federal court, an individual Indian could not expatriate himself from a tribe and adopt the habits of civilized life and thereby become a citizen of the United States. He needed a specific act of the United States admitting him to membership and citizenship.^3
So at this point, it essentially required an act of Congress for an Indian to become a citizen... Or did it? The answer: kinda.
In 1887, Congress passed the General Allotment Act, a piece of legislation that sought to downsize reservations across the country and create "surplus land" to sell off to rapacious settlers by creating land allotments of 160 acres that would then be given to each Indian/Indian family, with the remaining acreage of the total reservation becoming surplus. This piece of legislation, though, had a very interesting provision:
Edit: Grammar.