4 historic waves of immigration to USA
(numbers not official--depends on where you start)

1^st wave, 12-20,000 years ago, American Indians' Ancestors (During Ice Age, land exposed from Asia to Alaska)

2^nd wave 1600 - 1890 Northern Europe, 250,000 in 1700 > 50 million in 1890 [e. g., English, Germans, Scandinavians, Dutch, Scots-Irish, Irish
(near end of this wave; Catholic rather than Protestant like most earlier Northern European immigrants)

3^rd wave 1890-1924, Southern and Eastern Europe [e. g., Italians, Poles, Russians]; 1860s & 70s: Chinese; US population app. 100 million

[1920s-1960s: immigration severely restricted by racial quotas; in 1940s some Jews come to America to flee Holocaust despite tough immigration restrictions during this period]

4^th wave 1965- Latin America, West Indies, Eastern Europe, & Asia
US population in 1965: 200 million
US population in 2016: 323 million

Major U.S. laws restricting or liberalizing immigration

1882 Chinese Exclusion Act (repealed by Magnuson Act, 1943)

1892 Geary Act extends Chinese Exclusion Act, adding new restrictions on resident Chinese

1921 Emergency Quota Act, also known as the Emergency Immigration Act of 1921 (established quotas favoring immigrants from Western & Northern Europe, reducing immigration from Southern & Eastern Europe)

1965 Immigration and Naturalization Act created preference visa categories focused on immigrants' skills and family relationships with citizens or U.S. residents. The bill set numerical restrictions on visas at 170,000 per year, with a per-country-of-origin quota. However, immediate relatives of U.S. citizens and "special immigrants" had no restrictions. Opened immigration to Southern & Eastern Europe, Asia, Africa, South America, setting in motion profound shifts in USA's ethnographic mix.

1986 Immigration Reform and Control Act required employers to attest to their employees' immigration status, made it illegal to knowingly hire or recruit illegal immigrants, legalized certain seasonal agricultural illegal immigrants, and legalized illegal immigrants who entered the United States before January 1, 1982 [+ special conditions and requirements].

world population:

1800: app. 1 billion

1900: app. 1.7 billion

1950: 2.5 billion

1999: app. 6 billion

2008: 6.7 billion

est. 2050: 8.9 billion

est. 2150: 9.7 billion

Thomas J. Edsall,