The San Francisco Committee of Vigilance was formed in 1851, the catalyst for formation was the criminality of the Sydney Ducks, it was revived in 1856 in response to rampant crime and corruption in the municipal government of San Francisco, California. The need for extralegal intervention was apparent with the explosive population growth following the discovery of gold in 1848. The small town of about 900 individuals grew to a booming city of over 200,000 very rapidly. This overwhelming growth in population made it nearly impossible for the previously established law enforcement to regulate any longer which resulted in the organization of vigilantes.
These militias hanged eight people and forced several elected officials to resign. Each Committee of Vigilance formally relinquished power after three months.
The 1851 Committee of Vigilance was inaugurated on June 9 with the promulgation of a written doctrine declaring its aims and hanged John Jenkins of Sydney, Australia on June 10 after he was convicted of stealing a safe from an office in a trial organized by the committee: grand larceny was punishable by death under California law at the time. The June 13 Daily Alta California printed this statement:
It boasted a membership of 700 and claimed to operate in parallel to, and in defiance of, the duly constituted city government. Committee members used its headquarters for the interrogation and incarceration of suspects who were denied the benefits of due process. The Committee engaged in policing, investigating disreputable boarding houses and vessels, deporting immigrants, and parading its militia. Four people were hanged by the Committee; one was whipped (a common punishment at that time); fourteen were deported to Australia; fourteen were informally ordered to leave California; fifteen were handed over to public authorities; and forty-one were discharged. The 1851 Committee of Vigilance was dissolved during the September elections, but its executive members continued to meet into 1853.
A total of four were executed: John Jenkens, an Australian from Sydney accused of burglary, who was hanged on June 10, 1851; James Stuart, also from Sydney and accused of murder, who was hanged on July 11, 1851; and Samuel Whittaker and Robert McKenzie, associates of Stuart accused of "various heinous crimes", who were hanged on August 24, 1851. The lynching of Whittaker and McKenzie occurred three days after a standoff between the Committee and the nascent police force trying to protect the prisoners; the Committee nabbed Whittaker and McKenzie after storming the jail during Sunday church services.