In 1880, the city of San Francisco passed an ordinance that persons could not operate a laundry in a wooden building without a permit from the Board of Supervisors. At the time, about 95% of the city's 320 laundries were in wooden buildings. Approximately two-thirds of those laundries were owned by Chinese persons. Although most of the city's wooden building laundry owners applied for a permit, none were granted to any Chinese owner, while only one non-Chinese owner was denied a permit.
Yick Wo (Americanization: Lee Yick), who had lived in California and had operated a laundry in a wooden building for many years, continued to operate his laundry and was convicted and fined $10.00 for violating the ordinance. He sued for a writ of habeas corpus when he refused to pay the fine and was imprisoned in default of the fine.
However, the petitioner pointed out that prior to the new ordinance, the inspection and approval of laundries in wooden building had been left up to fire wardens. Yick Wo's laundry had never failed an inspection for fire safety. Moreover, the application of the prior law focused only on laundries in crowded areas of the city, while the new law was being enforced on isolated wooden buildings as well. The law also ignored other wooden buildings where fires were common - even cooking stoves posed the same risk as those used for laundry.
Yick Wo had little application shortly after the decision. In fact, it was not long after that the Court developed the "separate but equal" doctrine in Plessy v. Ferguson, 163 U.S. 537 (1896), in practice allowing discriminatory treatment of African Americans. Yick Wo was never applied at the time to Jim Crow laws which, although also racially neutral, were in practice discriminatory against blacks. However, by the 1950s, the Warren Court used the principle established in Yick Wo to strike down several attempts by states and municipalities in the deep south to limit the political rights of blacks. Yick Wo has been cited in well over 150 Supreme Court cases since it was decided.