During the first half of the 20th century, the U.S. saw rapid urban growth driven by industrialization and immigration, leading to the creation of jobs in cities. Immigrants, particularly from Europe, were often met with discrimination and faced challenges integrating into American culture, prompting anti-immigration sentiments. Labor unions emerged to protect workers against competition from low-skilled immigrant labor, while the melting pot theory suggested that diverse cultures would blend to create a new American society.