In the work, Roediger argued that "whiteness" is a historical phenomenon in the United States, as many different ethnicities now considered "white" were not initially perceived as such here. The Irish, for example, as Roman Catholics and from rural areas, were not considered "white" – meaning accepted as members of the Anglo-American Protestant majority society – until they began to distinguish themselves from black slaves and freedmen; from the New York Draft Riots of 1863, to riots in Philadelphia against black voting, and the Chicago Race Riot of 1919, ethnic Irish were prominent in violent confrontations against black Americans, with whom they competed for jobs, physical territory and political power. Roediger believes their struggle reflects the emergence of the modern theory of color consciousness, through which notions of "nations" and "races" were increasingly linked to color as the primary category of human difference. Roediger claims that the social construction of the concept of a white race in the United States was a conscious effort by slave owners to gain distance from those they enslaved, who were generally non-European and non-Christian. In addition, white working peoples gained distance from their Southern proletarian complements, the slaves. By the 18th century, he says, "white" had become well-established as a racial term in the United States; by the end of the 19th, it had become an all-encompassing one.