It was said that during the last half of the 19th century more of San Francisco's workers enjoyed an eight-hour workday than any other American city. The molders' and boilermakers' strike of 1864 was called in opposition to a newly formed iron-works employers association which threatened a one thousand dollar a day fine on any employer who granted the strikers' demands and had wired for strikebreakers across the country. The San Francisco Trades Union, the city's first central labor body, sent a delegation to meet a boatload of strikebreakers at Panama and educated them. They arrived in San Francisco as enrolled union members.