Diversity was inevitable in the United States during the transition of the 19th and 20th centuries. This amount of diversity made the United States the nation it is today, however, it did not develop very easily. African Americans were present in the United States as a result of slavery. On the other hand, before the Mexican-American War, citizens of Mexico were previously living on land that is now part of the United States. These two specific racial groups were viewed as inferior by others who supported white supremacy which resulted in opposing views between the races. With these views, discrimination, segregation, and eventually reform emerged. During the late 19th century and early 20th century, the civil and political rights of African Americans and Mexican Americans were restricted which led to reforms that benefitted the involvement and equal opportunities of those minorities.
The idea of race is part of the reason why African Americans and Mexican Americans struggled to be included and treated equally, socially and politically. One may argue that race is determined biologically, but, in fact, it is socially constructed. In American Government In Black And White Mcclain and Tauber said, "The designation of a person's race in the United States has historically been decided by American society's desire to exclude groups of people from participation in the social and political life of the nation."(127). The idea of race gives the United States the ability to categorize different groups of people based on their appearance. This results in stereotypes and discrimination against different groups. Segregation played a role in the inequality of African Americans and Mexican Americans which also made it extremely difficult for these racial groups to be included and treated equally, socially and politically. .
In 1862, Abraham Lincoln established the Emancipation Proclamation which abolished slavery.