In the eighteenth and nineteenth century, the metaphor of a (s)melting pot was used to describe the fusion of different nationalities, ethnicities and cultures.
It was used together with concepts of the United States as an ideal republic and a "city upon a hill" or new promised land.
It was a metaphor for the idealized process of immigration by which different nationalities, cultures, nationality, ethnicity and race were to blend into a new community /society.
The ethnic mosaic or the salad bowl concept suggests that the integration of the many different cultures of United States residents combine like a salad, as opposed to the melting pot.
In the ethnic mosaic or the salad bowl model, various American cultures are juxtaposed — like salad ingredients — but do not merge into a single homogeneous culture. Each culture keeps its own distinct qualities. This idea proposes a society of many individual, "pure" cultures in addition to the mixed culture that is modern American culture, and the term has become more politically correct than melting pot, since the latter suggests that ethnic groups may be unable to preserve their cultures due to assimilation.