On Mexico's northwestern frontier, judicial conflicts unfolded against a backdrop of armed resistance and ethnic violence. In the face of Apache raids in the north and Yaqui and Mayo revolts in the south, domestic disputes involving children, wives, and servants were easily conflated with ethnic rebellion and ""barbarous"" threats. A wife's adulterous liaison, a daughter's elopement, or a nephew's enraged assault shook the very foundation of what it meant to be civilized at a time when communities saw themselves under siege. Laura Shelton has plumbed the legal archives of early Sonora to reveal the extent to which both court officials and quarreling relatives imagined connections between gender hierarchies and civilized order. As she describes how the region's nascent legal system became the institution through which spouses, parents, children, employers, and servants settled disputes over everything from custody to assault to debt, she reveals how these daily encounters between men and women in the local courts contributed to the formation of republican governance on Mexico's northwestern frontier. Through an analysis of some 700 civil and criminal trial records--along with census data, military reports, church records, and other sources--Shelton describes how courtroom encounters were conditioned by an Iberian legal legacy; brutal ethnic violence; emerging liberal ideas about trade, citizenship, and property rights; and a growing recognition that honor--buenas costumbres--was dependent more on conduct than on bloodline. For Tranquility and Order offers new insight into a legal system too often characterized as inept as it provides a unique gender analysis of family relations on the frontier.