 By the early 1880s, the population had adopted the term Tong war to describe periods of violence in Chinatown, the San Francisco Police Department had established its so-called Chinatown Squad.The anti-immigrant sentiment became law as the United States Government passed the Chinese Exclusion Act of 1882 – the first immigration restriction law aimed at a single ethnic group.This law, along with other immigration restriction laws such as the Geary Act, greatly reduced the number of Chinese people allowed into the country and the city, and in theory limited Chinese immigration to single men only.