By 1920, Detroit had become the fourth-largest city in the United States, with an industrial and population boom driven by the rapid expansion of the automobile industry. In this era of continuing high immigration from southern and eastern Europe, the Ku Klux Klan in the 1920s established a substantial presence in Detroit during its early 20th-century revival. The KKK became concentrated in midwestern cities rather than exclusively in the South. It was primarily anti-Catholic and anti-Jewish in this period, but it also supported white supremacy.