America has the largest number of immigrants in the world. In the 19th and early 20th centuries, large numbers of Southern Europeans and African Americans moved to American cities. This is the third wave of immigration in the history of the United States. There are both push and pull factors that bring them here. Most of them faced many difficulties and challenges when they first came here. However, depending on their race or ethnicity, some of them get great opportunities, so they experience greater social mobility and live a better life. In the 19th century, approximately 20 million European immigrants arrived in America. There are various reasons why they come here and these reasons can be separated into push and pull factors. The first push factor is that industrialization is growing rapidly across Europe and destroying the traditional economy. This event is also called the “Great Migration”. There are several push and pull factors that lead to this event. The main push factor is the “Kim Crow Law”. Most African Americans faced racial segregation. They have to drink from different fountains, use different bathrooms, and sit in the back of the bus or train. It is also difficult for them to find work in the South, because most jobs are open to whites. It is difficult for them to be financially successful. There is also a lot of violence against blacks, such as lynching. The first pull factor is the many job opportunities, because there are many demands from the war, so the war industries need many people. Most factories at that time faced a labor shortage. The second pull factor is that the wages and living conditions are much better than in the South. The third factor is that blacks can vote in the North, so they can gain political power. The fourth factor is that in the North there is not much segregation compared to the South and not much violence either. The last factor is that they have more freedom in the