Definition
A fort is a fortified place protected from attack by structural means — such as a moat, wall, parapet, stockade, or rampart — occupied by military troops. In legal usage, the term carries a specific threshold: it denotes something more than a mere military camp, post, or station. The presence of physical fortification is the defining characteristic. A temporary encampment or administrative military post does not qualify; structural defense works are required.
The distinction matters primarily in the context of federal land law, military jurisdiction, and property statutes that treat forts as a recognized category of public land or federal installation.
Common Language
Modern common usage (Wiktionary): A fortified defensive structure stationed with troops; any permanent army post; an outlying trading station; or, informally, a structure improvised from furniture and bedding for play.
Historical common usage (Webster's 1913): A strong or fortified place; usually a small fortified place occupied only by troops, surrounded with a ditch, rampart, and parapet, or with palisades, stockades, or other means of defense.
The legal definition tracks closely with the military and architectural sense — but with a meaningful refinement. Everyday usage treats "fort" and "military post" as interchangeable, and modern informal use has further diluted the word. Legal sources reject that equivalence explicitly: a post or station without fortification does not qualify. A researcher reading a statute or land grant that references a "fort" should not assume any permanent military presence counts.
Core Elements
The historical dictionaries converge on a two-part threshold for legal recognition as a fort:
1. Physical fortification: The site must have structural defensive works — moat, wall, parapet, stockade, rampart, or equivalent means of protection against attack. The nature of the works matters; improvised or temporary shelters do not satisfy this element.
2. Military occupation: The fortified structure must be garrisoned or occupied by troops. An abandoned fortification or a civilian defensive structure does not automatically constitute a fort in the legal sense.
Both elements must be present. A military camp without fortification is merely a camp. A walled structure without military function is not a fort.
Why It Matters in Research
The legal definition of fort surfaces most often in two research contexts: federal public land law and military jurisdiction statutes.
In public land law, federal statutes and land grants frequently distinguished between classes of military land — forts, reservations, camps, and posts — with different legal consequences for each. Whether a given installation qualified as a "fort" could determine the scope of federal authority over surrounding lands, the applicability of cession statutes, or the terms under which land reverted to state or private ownership after military abandonment. Researchers working with 19th-century federal land records, particularly in the western territories, should verify whether a named installation met the structural threshold before assuming statutory provisions applicable to "forts" apply.
The related term FORTALICE — noted in Bouvier — refers to a fortress or place of strength that historically required a special grant to pass in conveyance. Though largely obsolete, it appears in older English title chains and may surface in colonial-era land records.
Jurisdictional questions around forts also implicate the enclave doctrine: Congress has exclusive legislative jurisdiction over lands ceded by states for federal military purposes, and whether a site constituted a proper fort could bear on whether that cession had occurred. Researchers tracing the legislative history of military lands should cross-reference the land status records of the specific installation, not simply assume that any named "Fort X" carried fort-level legal status at all relevant times.
The Anderson's cross-reference to LAND, Public is a useful pointer: fort classifications appear within the broader taxonomy of public lands, and researchers in that area should follow that thread.
Historical Dictionary Support
All four source dictionaries agree on the essential formulation: a fort implies something more than a military camp, post, or station, and requires actual fortification by structural means. The language is nearly identical across Black's (both editions), Anderson's, and Bouvier's — all appear to draw from or track U.S. v. Tichenor, 12 Fed. 424, the case from which the quoted language originates.
Bouvier adds the related entry FORTALICE, which the other dictionaries omit. This is a meaningful gap: fortalice carried distinct conveyancing implications in English and early American law and is worth noting for researchers working with older title records or colonial land grants.
None of the historical dictionaries address the trading-post usage that Wiktionary records — the sense of "fort" as an outlying commercial station common in the fur trade era of British North America. That usage was legally significant in certain property and jurisdictional contexts in the northern territories and early Canadian law, but it falls outside the scope of these American legal dictionaries.
Jurisdictional Note
The legal definition of fort is primarily a federal question in American law, arising in the context of federal military installations and public land classifications. State law rarely defines the term independently. Researchers working in Canadian or British colonial legal history should be alert to the trading-post usage of fort, which carries different legal implications than the military-fortification definition dominant in U.S. sources.