1900-1920

• First decade of 20th century saw peak explosion.
• Character of land changed from farm living to city living.
• WW1 slowed immigration.

1920-1940

• Unemployment, congestion.
• Congress reduced immigration number.
• First half of decade added to record high growth.
• 1930's-depression reduced growth.

1940-1960

1960-1980

• The growth rate at the end of the decade was a 3rd lower than at the beginning.
• A vigorous social and political movement emerged calling for Americans to keep their fertility of a replacement to enable the country to eventually stabilize its population.
• Numerous experts and commentators predicted that each decade would see lower and lower population growth until early in the 21st century there would be no growth at all.

1980-2000

• The reason was that congress had created a system of a chain migration the SnowBalled and doubles annual legal immigration over traditional levels.
• Federal immigration policy was negating the results of Americans' choosing to have smaller families.
• Although American-born citizens maintained a below-replacement-level fertility rate, immigrant fertility was at a similar rate to the U.S. Baby Boom fertility of the 1950s.

2000-2010

• Mass immigration continued during the first decade of the new century.
• Mass amnesty bills failed in the senate on multiple occasions, leading to the drafting of more focused amnesty legislation including DREAM Act.
• The 2010 mid-term elections saw a dramatics shift in the immigration Balance of power in congress, increasing chances for legislation that would reduce overall numbers.