Racial segregation by businesses during Jim Crow was often voluntary and practiced without a legal mandate. Voluntary segregation can be driven by profit-motivated business owners catering to racist white customers or discrimination by business owners. We assess the relative importance of customers’ and firms’ discrimination by examining the 1953 desegregation of Washington, DC, movie theaters, which occurred rapidly because of a Supreme Court ruling affecting only businesses in Washington. Using weekly data for a nationwide sample of theaters, we find that revenues of Washington theaters fell relative to other theaters, consistent with reduced demand from biased white customers. We use a test for firms’ discrimination based on a model of the screening decision for films with black actors cast in prominent roles. We cannot reject that the run length of these films was profit motivated. Together, our results point toward customer discrimination as a primary cause of public accommodation segregation