"The United States has received about 75 million immigrants since record-keeping began in 1820. This relatively open door was due to a confluence of interests, both external and internal. As modernisation spread throughout the Old World during the 18th and 19th centuries, the (relatively) open frontier beckoned the landless and others seeking economic betterment. These patterns culminated in the early 20th century, when more than one million immigrants arrived annually—a level that is only being rivaled by contemporary levels of immigration. American economic and political institutions also gained from immigration. Immigrant settlement helped to secure the frontier as well as to provide labour for nation-building projects, including transportation networks of roads, canals, and railroads. During the era of industrialisation, immigrant labour provided a disproportionate share of workers for the dirty and dangerous jobs in mining and manufacturing (Hirschman and Mogford 2009). In spite of the national tradition of mass immigration, new arrivals have rarely received a welcome reception. The conservative backlash against immigrants has been a perennial theme of American history. During the Age of Mass Migration, the negative reaction against immigrants was not simply a response from the parochial masses, but also a project led by conservative intellectuals. Long before immigration restrictions were implemented in the 1920s, there was a particularly virulent campaign against the ‘new’ immigrants from Eastern and Southern Europe. Most of these immigrants were Catholics and Jews—religious and cultural traditions that were thought to be in conflict with the traditional ascendancy of white Protestants of English ancestry. As most Northeastern and Midwestern cities became dominated by immigrants (both first and second generations) in the late 19th century, many elite old-stock American families and communities created barriers to protect their ‘aristocratic’ status and privileges against newcomers (Higham 1988). Residential areas became ‘restricted,’ college fraternities and sororities limited their membership, and many social clubs and societies only allowed those with the right pedigrees and connections to be admitted (Baltzell 1964). Barriers to employment for minorities, especially Jews, were part of the culture of corporate law firms and elite professions (Auerbach 1975: Chap. 2). In the early 20th century, many elite private universities were notorious for their quotas for Jewish students and their refusal to hire Jews and other minorities (Baltzell 1964: 336; Karabel 2006). In some cases, these quotas persisted until the 1960s."