Liberty Hill site in San Pedro, Los Angeles, California was the site of the 1923 strike by the Marine Transport Workers Industrial Union 510 a part of the Industrial Workers of the World (IWW). The strike was called to draw attention to the worker's low wages and poor working conditions. It was also to draw attention to some union activists that had been arrested and lockup for violating the California Criminal Syndicalism Act passed on April 30, 1919, by Governor William Stephens, which criminalized syndicalism. The strike tied up 90 ships in Port of Los Angeles San Pedro. The Liberty Hill site was designated a California Historic Landmark on March 3, 1997.