Results show that a proxy measure of the presence of Scotch-Irish communities in the Old South, namely, the percentage of churches that were Presbyterian in 1850 is positively related to contemporary White male homicide offending that arises out of arguments, when evaluated for units with greater numbers of cattle and pigs per capita in 1850, and controlling for a wide array of contemporary and historical predictors of homicide. Also found was that argument-related homicide occurred with less frequency in parts of the South that were more dependent on the production of crops in 1850. Considered as a whole, these findings are supportive of theoretical claims about the role of herding as the ecological underpinning of a code of honor. The differential reliance on slavery in 1850 serves primarily as a control variable in the analysis to address concerns about a spurious effect of herding; nevertheless, a substantively important finding for this variable was detected. Slavery is positively related to contemporary homicide offending by White men, and may be driven by a negative effect of slavery on offending by African Americans. Future research should test the herding thesis by studying other geographies, other outcomes, and other types of livestock, as deemed pertinent to the theory. Data were collected from 497 counties and county clusters in 12 southern States. Table, figure, appendixes, notes, and references