Definition
In legal contexts, Mormonism refers to the social and religious system associated with the Church of Jesus Christ of Latter-day Saints, as treated by law primarily through the lens of polygamy — the practice of plural marriage that characterized early Latter-day Saint communities. In nineteenth and early twentieth century American law, "Mormonism" functioned less as a theological designation and more as a shorthand for the legal problem of plural marriage, which federal and territorial statutes prohibited as bigamy. The term appeared in legal sources not as a comprehensive religious classification but as a site of conflict between religious practice and civil law, particularly in the Territory of Utah.
Common Language
Modern common usage (Wiktionary): The religious, ideological, and cultural aspects of the various denominations of the Latter-day Saint movement; a religion evolved out of Christianity founded by Joseph Smith, whose members regard the Book of Mormon as scripture.
Historical common usage (Webster's 1913): The doctrine, system, and practices of the Mormons.
The gap between common and legal meaning is significant. In ordinary usage — both historical and modern — Mormonism describes a religion in full: theology, scripture, community, and practice. In legal sources of the same era, the term was functionally reduced to a single practice: polygamy. Historical legal dictionaries treated Mormonism as synonymous with plural marriage and its consequences under law, stripping away the broader religious content that defines the term in every other context. Researchers must read historical legal uses of "Mormonism" as the law's characterization of a specific contested practice, not as a neutral description of a religious community.
Common Confusion
Mormonism as a legal term should not be confused with polygamy as a general legal category. The historical legal treatment of Mormonism was specific to the American federal-territorial context and the anti-polygamy legislation targeting Latter-day Saint communities. General polygamy law existed independently and applied to conduct without religious dimension. Conversely, the constitutional dimension of Mormonism cases — the tension between the Free Exercise Clause and federal criminal prohibition — is distinct from polygamy prosecutions that raised no religious liberty questions. The two threads (criminal prohibition and constitutional religion-clause analysis) run together in the historical record but are analytically separate.
Why It Matters in Research
This term is a product of a specific historical moment and should be treated as a period artifact, not a stable legal category.
Corpus researchers should be alert to several traps. First, historical legal dictionaries define Mormonism almost entirely through the polygamy problem, which means that any broader legal treatment of Latter-day Saint religious practices — property rights of the church, disincorporation proceedings, disenfranchisement of members — will not be indexed under this term. Researchers investigating the full legal campaign against the Church of Jesus Christ of Latter-day Saints in the territorial period must also search under POLYGAMY, BIGAMY, CHURCH PROPERTY, and DISINCORPORATION.
Second, the legal definition reflects a territorial rather than a state context. Most primary sources using this term date to the period before Utah statehood in 1896, when Congress exercised plenary authority over territorial law. After statehood, the legal framing shifted; "Mormonism" as a legal category largely dissolved because the specific federal-territorial mechanism that produced the case law ceased to operate.
Third, the constitutional dimension of these cases — whether criminal prohibition of religiously motivated plural marriage violated the Free Exercise Clause — produced significant early Supreme Court doctrine. The line of cases beginning with Reynolds v. United States (1879) established the belief-action distinction that governed Free Exercise jurisprudence for generations. Researchers working on religion-clause history will find that the legal treatment of Mormonism is foundational to that field, but the connection is not visible from the dictionary entries, which focus narrowly on the criminal law dimension.
Fourth, English legal sources treat the question differently. Rapalje & Lawrence note that plural marriages are not recognized by English law and cite English precedent, which reflects a conflict-of-laws framing: courts asked whether Mormon plural marriages contracted in Utah had legal effect in England or other jurisdictions. This is a distinct research thread from the American criminal prohibition.
Historical Dictionary Support
The five source dictionaries show a narrow consensus with minor variation. Black's (1st and 2nd editions) are identical, defining Mormonism as a social and religious system with polygamy as its legally relevant feature, and noting that plural marriages are indictable offenses under federal and Utah territorial statutes. Rapalje & Lawrence add English legal citations and note that English law also refuses recognition to such marriages — a conflict-of-laws perspective absent from the American sources. Bouvier offers a slightly fuller formulation, referencing doctrines, practices, ceremonies, and church government, but still leads with polygamy. Anderson dispenses with independent treatment entirely, redirecting to POLYGAMY.
What the historical dictionaries collectively miss is substantial. None addresses the constitutional religion-clause litigation that made Mormonism legally significant beyond the criminal context. None addresses the Edmunds Act (1882) or the Edmunds-Tucker Act (1887), which disincorporated the Church, escheated its property, and disenfranchised members — legal developments that extended far beyond the polygamy prosecution framework their definitions describe. None reflects the post-1890 period after the Church renounced plural marriage, when the legal category became largely obsolete. Researchers relying solely on these dictionary entries will have a severely truncated picture of the actual legal history.
Jurisdictional Note
The legal content of this term is almost entirely American and, within the United States, almost entirely federal and territorial. English law treated the question as one of marriage recognition rather than criminal prohibition. After Utah statehood and the Church's renunciation of polygamy, "Mormonism" as a functional legal category ceased to develop. Modern law does not use the term as a legal classification.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia: Polygamy; Free Exercise of Religion; Federal Territorial Authority