Definition
The legal status of a person born to parents who were not lawfully married to one another at the time of birth. Historically, illegitimacy was a formal legal classification with sweeping consequences: a child born outside of marriage was deemed a "bastard" in law, with no recognized paternal lineage, no right to inherit through the father, no claim to the father's name or support, and reduced standing in legal proceedings. The status attached to the child, not the parents, and followed the individual through life.
Over the course of the twentieth century, illegitimacy as a legal category was substantially dismantled in most common law jurisdictions. Constitutional equal protection doctrine — particularly the line of Supreme Court decisions beginning in the late 1960s and running through the 1980s — progressively invalidated state laws that imposed legal disabilities on children solely on the basis of their parents' marital status at birth. The term itself has largely been retired from modern statutes and judicial opinions, replaced by "nonmarital child," "child born outside of marriage," or similar neutral formulations. The underlying substantive questions — paternity establishment, inheritance rights, parental rights and obligations — persist, but are now addressed through frameworks that do not formally penalize the child for the circumstances of birth.
Common Language
Modern common usage (Wiktionary): The state of being illegitimate; also, the state of being born to parents not legally married to each other.
Historical common usage (Webster's 1913): The state of being illegitimate.
The common usage of "illegitimacy" has always tracked the legal meaning closely, because the legal category itself created the social stigma. The ordinary-language sense is not independent of the legal one — it derives from it. Researchers should note that in nonlegal contexts today, the word often carries a different primary meaning (something lacking authority or legitimacy in a general sense), while the birth-status meaning has retreated from both law and everyday usage. When "illegitimacy" appears in historical texts, it almost certainly refers to the legal status; in contemporary texts, context is required to determine which sense is intended.
Common Confusion
Illegitimacy is sometimes conflated with bastardy, which was the older common law term for the same condition. The two are functionally synonymous in historical sources, but "bastardy" carried explicit procedural connotations — bastardy proceedings were the formal legal mechanism for determining whether a child was illegitimate and for establishing paternal obligations. Illegitimacy describes the status; bastardy often appears in the context of the proceeding. Researchers encountering either term in historical documents should treat them as referring to the same underlying legal classification. See BASTARDY; BASTARD.
Why It Matters in Research
Illegitimacy is a term in profound transition, and the period of that transition — roughly 1968 to 1990 in U.S. federal constitutional law — is a significant fault line in the corpus. Sources from before that period treat illegitimacy as an operative legal category with fixed consequences. Sources from within the transition period reflect active constitutional litigation and legislative reform. Sources from after it largely avoid the term altogether while still resolving the same practical questions under new frameworks.
Several traps await the historical researcher. First, the word "illegitimate" appears in historical statutes and cases in ways that sound categorical and permanent, but the legal rules those sources describe were subsequently invalidated or superseded. A researcher relying on pre-1970 sources to understand a child's inheritance rights, for example, may be reading law that no longer reflects the applicable rule. Second, the shift away from formal illegitimacy did not eliminate all distinctions between marital and nonmarital children — it changed the grounds and the burden. Establishing paternity for a nonmarital child, triggering inheritance rights, and determining parental obligations all still require affirmative legal steps that are not required when a child is born to married parents. Third, jurisdictional variation remains significant: the pace and scope of legislative reform varied considerably across states, and international sources still use the vocabulary and sometimes the substantive rules of traditional illegitimacy law.
The corpus connection between illegitimacy and equal protection doctrine is especially important. Cases involving illegitimacy classifications were a primary vehicle through which intermediate scrutiny concepts were debated and shaped in constitutional law. Researchers working on equal protection, suspect classifications, or the evolution of constitutional family law will find illegitimacy doctrine central to that history.
Historical Dictionary Support
All three source dictionaries define illegitimacy in substantially identical terms: the condition or social status of one whose parents were not married at the time of birth. Black's (both editions) and Bouvier's converge on this formulation without variation, reflecting that the term had a settled, uncontested meaning at the time those dictionaries were compiled.
What the historical dictionaries do not reflect — because they predate it — is the constitutional transformation of the field. Neither edition of Black's nor Bouvier's signals that illegitimacy as a legal category would be subjected to heightened constitutional scrutiny, progressively narrowed, and ultimately abandoned as an organizing legal concept. Read in isolation, these entries suggest a stable, permanent status. That impression is historically accurate for their era but misleading if applied to modern law.
The citation in Black's 2nd Ed. to Miller v. Miller and Brown v. Belmarde illustrates how state courts were then applying the classification in inheritance and family law disputes — routine applications of a then-settled rule. Those cases are now primarily of historical interest.
Jurisdictional Note
The constitutional floor set by federal equal protection doctrine applies throughout the United States, but state law governs the specific mechanisms for establishing paternity, determining inheritance rights of nonmarital children, and adjudicating parental rights. Several states moved earlier and further than federal constitutional doctrine required; others moved only as compelled. Researchers working across jurisdictions should verify the applicable state statutory framework rather than assuming uniform treatment. In civil law jurisdictions and in much of international family law, formal categories of legitimacy and illegitimacy persist in some form, though the trend toward abolition is widespread.
Encyclopedia Cross-Reference
Law Mind Encyclopedia — Legitimacy and Parentage
Law Mind Encyclopedia — Equal Protection and Classifications
Law Mind Encyclopedia — Intestate Succession and Inheritance