Sex and Privacy in American Law presents empirical analyses of civil and criminal state court decisions applying the U.S. Supreme Court's landmark decision in Lawrence v. Texas. After tracing key historical and legal developments leading up to the Lawrence decision's decriminalization of sodomy on substantive due process grounds in 2003, the study employs both quantitative and qualitative content analyses of 307 cases citing Lawrence over the two decades since it was decided. Results indicate that judicial decisions rarely embraced broad readings of Lawrence in criminal cases. In fact, Lawrence's long-term impact on criminal law has largely remained as limited as some commentators predicted shortly after the case was decided. In civil cases, courts tended not to rely on Lawrence significantly in most business and employment law cases. Courts that applied Lawrence in family law disputes – especially those involving same-sex couples – often construed the case narrowly at first, but broadened their interpretations after Obergefell v. Hodges brought marriage equality to the United States. Lawrence also impacted LGBTQ+ civil rights claims. Statistically significant geographic differences were found relating to how courts used Lawrence in those cases, with judges in Northeastern and Pacific coastal states having applied the precedent broadly, while judges in Southern and Midwestern states tending to have applied the case more narrowly. The implications are explored generally and within the specific context of the constriction of substantive due process rights in the wake Dobbs v. Jackson Women's Health Organization.