In the 19th century, this was particularly true because of anti-Irish prejudice, which was based on anti-Catholic sentiment, and prejudice against the Irish as an ethnicity. This was especially true for Irish Catholics who immigrated to the U.S. in the mid-19th century; the large number of Irish (both Catholics and Protestants) who settled in America in the 18th century had largely (but not entirely) escaped such discrimination and eventually blended into the white American population. During the 1830s in the U.S., riots over control of job sites broke out in rural areas among rival labor teams whose members were from different parts of Ireland, and riots also broke out between Irish and local American work teams which were competing for construction jobs.