From the Guidebook:
In 1923 the Marine Transport
Workers Industrial Union 510, a branch of the Industrial
Workers of the World (IWW), called a strike that immobilized
90 ships here in San Pedro. The union protested low wages,
bad working conditions, and the imprisonment of union
activists under California's Criminal Syndicalism Law.
Denied access to public property, strikers and their supporters
rallied here at this site they called "Liberty Hill."
Writer Upton Sinclair was arrested for reading from the
Bill of Rights to a large gathering. The strike failed
but laid a foundation for success in the 1930s. The Syndicalism
Law was ruled unconstitutional in 1968.