We compare homicides in San Francisco during the Gold Rush (1849-1860) to homicides in later years when homicide rates were much lower. Our evidence suggests that the homicide epidemic during the gold rush was primarily due to a higher incidence of disputes between unrelated persons, including duels and conflicts over land, mining claims, and gambling. Unlike a more recent epidemic (1965-1980), the Gold Rush did not involve particularly high rates of predatory or domestic homicides. The fact that only one type of homicide increased during the Gold Rush suggests that the epidemic was not due to a decline in formal or informal social control. San Francisco had a professional police department, a well-regulated city prison, and a strong vigilante organization during this period.
Our results suggest that situational factors associated with violence change over time and affect frequency. Homicides during the gold rush were much more likely to involve intoxicated men than homicides during other time periods. Homicides during both epidemics were much more likely to involve weapons. Knives were the weapon of choice during the gold rush while firearms were prevalent in the more recent epidemic. Our research, along with previous research, suggests that it is primarily armed violence that varies across time and space. Unarmed violence (e.g., fist fights) is ubiquitous. So is domestic violence, as the domestic homicide rate did not change much over the 154 year period.
Our results suggest that the role of interpersonal conflict deserves more attention in the study of violence. Violence is likely to be more frequent when communities and individuals experience more disputes. The results also show the importance of determining what exactly needs to be explained when studying violence. Is it variation in crime, violence, or a particular type of violence that we are trying to explain, for example? Establishing the proper dependent variable narrows down the possible theoretical explanations.