Throughout American history, African Americans and other minority groups, with and without white allies, have combated racial discrimination using a variety of tactics. These have included public protests, such as street picketing and riots; organized publicity campaigns; educational efforts; and litigation. They have also included efforts at economic self-help through voluntary organizations such as the National Urban League. For example, in New York City during the Great Depression, the League sponsored the "Don't Buy Where You Can't Work Campaign," picketing and boycotting white-owned businesses that had primarily black customers but discriminated against blacks in employment. These protests spread to other cities, and in 1937 the Supreme Court upheld the protesters' right to peacefully picket.