How many large-scale immigrants formed the foundation of American culture?

Four times. The United States is a typical immigrant country, and its history can be traced back to 1620. There have been four large-scale immigrants in American history. The first time was 1820- 1860, and the number of immigrants was as high as 5 million. The second time was 186 1- 1880. After the end of the Civil War, the United States ushered in the peak of industrialization, and the demand for labor was great. The total number of immigrants exceeds 5 million. The third time 188 1- 1920 The industrialization and urbanization of the United States are accelerating, and the demand for labor is large. The fourth immigrant 1965. Talent introduction and reunion of American citizens.