Definition
A government establishment charged with the receipt, handling, and delivery of mail. In legal usage, the term encompasses both the physical location where postal operations are conducted and, more broadly, the institutional framework of the federal postal system. The post office is an arm of the federal government, and its operations, jurisdiction, and the infrastructure supporting mail delivery carry significant legal consequences — particularly in federal criminal law, constitutional law, and regulatory matters.
The legal significance of the term extends beyond the building or office itself. Legally designated "post roads" — the routes over which mail travels — form a key jurisdictional boundary. Courts and statutes have defined post roads expansively to include city streets used by letter carriers, all public roads and highways maintained as such, all railroads, and navigable waters, canals, and plank roads of the United States while the mail is carried over them. This broad definition has direct implications for federal jurisdiction over crimes committed in connection with mail.
Common Language
Modern common usage (Wiktionary): An alternative form of "post office" — a public facility where mail and packages are received, sorted, and distributed, and where postal products and services are sold.
Historical common usage (Webster's 1913): An office under governmental authority where letters, packets, and other mail matter are received and distributed; also, the governmental system by which mail is collected and transmitted.
The gap between common and legal meaning here is largely one of scope rather than kind. Ordinary usage focuses on the physical location. Legal usage extends the concept outward to encompass the network of post roads, the federal jurisdiction that attaches to mail in transit, and the regulatory and criminal law consequences that follow. A researcher treating "post office" as merely a building will miss the jurisdictional reach of postal law.
Why It Matters in Research
The term appears most critically in federal jurisdiction questions. Because mail routes — including ordinary city streets, railroads, and waterways — qualify as post roads, conduct affecting the mail can trigger federal authority even when the act occurs far from any post office building. Researchers working with 19th- and early 20th-century materials should be alert to this expansive definition, which was actively litigated and shaped by congressional postal legislation.
In historical sources, the term "post office" and "postoffice" are used interchangeably; Bouvier's renders it as one word, while modern usage splits it. When searching historical digests, case reporters, and statutory compilations, use both forms.
Federal criminal law built heavily on the postal infrastructure — mail fraud, obstruction of correspondence, and related offenses all derive their federal character from the connection to the post office and post roads. Researchers tracing the development of federal criminal jurisdiction will find the post road definition a foundational concept.
The institutional identity of the post office also shifted significantly in 1971, when the United States Post Office Department (a Cabinet-level agency) was reorganized into the United States Postal Service, an independent establishment of the executive branch. Legal materials before and after this reorganization use different institutional names and operate under different statutory frameworks. Sources citing the "Post Office Department" refer to the pre-1971 entity; post-1971 materials reference the USPS. This distinction affects which regulations, cases, and administrative decisions are controlling for a given research question.
Historical Dictionary Support
Bouvier's Law Dictionary provides the clearest synthesis of the legal concept as it developed through the 19th and early 20th centuries. Bouvier emphasizes the post road definition and its breadth — a definition shaped by federal courts interpreting congressional power under the Postal Clause of the Constitution (Article I, Section 8). The references in Bouvier to specific reporters and supplements reflect an era when the reach of post road jurisdiction was actively contested and expanded through litigation involving railroads, waterways, and urban street systems.
What Bouvier's does not address, and what later legal development required, is the administrative law dimension — the post office as a regulatory body with rulemaking authority, and the criminal law superstructure that developed around mail fraud and related offenses in the late 19th century. Researchers should treat Bouvier's entry as a foundation for jurisdictional questions but supplement it with statutory and case law research for regulatory and criminal dimensions.
Jurisdictional Note
The post office is exclusively a federal institution in the United States; there is no state-level equivalent with comparable legal authority. Jurisdictional questions arising from postal operations are federal questions. However, state law may interact with postal matters in areas such as property rights in post office buildings and labor law applicable to postal workers.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia — Postal Law; Federal Administrative Agencies; Federal Criminal Jurisdiction