This document discusses how Social Darwinism influenced US immigration policy between 1880-1925. It summarizes how Herbert Spencer first articulated Social Darwinism, which applied concepts of "survival of the fittest" to human society. However, Social Darwinism differed fundamentally from Charles Darwin's scientific theory by rejecting randomness and attributing success to inherent traits. Still, Social Darwinism gained legitimacy by associating with Darwin's work. The document then discusses how Social Darwinism was used to justify increasingly restrictive immigration laws targeting certain ethnic groups, like the Chinese Exclusion Act of 1882, based on ideas of racial superiority and fears that immigrants threatened American civilization and economic opportunities.