Under the Articles of Confederation, Congress possessed the power to establish and regulate post offices. The Framers easily transferred the power into the Constitution and gave Congress the additional authority to establish postal roads. At the Constitutional Convention, Benjamin Franklin (who had been appointed Postmaster General in 1775 by the Second Continental Congress) suggested that, in addition to establishing post roads, Congress should have the “power to provide for cutting canals where deemed necessary,” and James Madison sought to enlarge the power “to grant charters of incorporation where the interest of the U.S. might require the legislative provisions of individual States may be incompetent.” However, the Founders turned aside these extensions on the ground that such powers were already assumed in the power to regulate trade.

Following the adoption of the Constitution, the Act of September 22, 1789 (1 Stat. 70) established (at first temporarily) a post office and created the Office of the Postmaster General. By that time, seventy-five post offices and over 2000 miles of post roads already existed. What was originally thought to be a rather simple and benign power soon turned controversial; there was disagreement over whether this power merely enabled Congress to direct where post offices should be located and on what roads mail should be carried, or whether it authorized Congress to construct and maintain roads and post offices within the states. Thomas Jefferson and James Monroe doubted whether the clause granted Congress the power to construct roads, whereas many in Congress asserted that it did have such power. In fact, most congressional enactments merely designated post roads, but in 1833, Justice Joseph Story declared in his Commentaries on the Constitution of the United States that the words “to establish” encompass a power to create roads as well as to designate them. Story maintained, however, that once built, a post road is subject to the laws of the state. In 1845, in the case of Searight v. Stokes, Chief Justice Roger B. Taney held that mail carriages were immune to state road taxes on the Cumberland Road (part of the National Road), but, over the dissent of Justice Peter V. Daniel, he specifically avoided the question of the power of Congress to construct post roads.

Story’s view has stronger textual support than does Jefferson’s. The power “to establish an uniform Rule of Naturalization, and uniform Laws on the subject of Bankruptcies” (Article I, Section 8, Clause 4), and the power of Congress to “establish” inferior federal courts (Article III, Section 1) clearly contemplate the creation of such laws and courts, respectively. Congress would seem to have a similar creative power in establishing post roads.

A second point of contention was the question whether Congress could delegate the designation of post offices (most of which were in existing institutions, such as general stores or inns) and post roads. The First Congress debated the issue and resolved it with the Postal Service Act of 1792, which provided a detailed list of post offices and post roads, keeping the power in Congress’s hands and becoming a principal means for Members to patronize their home districts until the Postal Reorganization Act of 1970. That Act transformed the Post Office Department, which had been a tax-subsidized cabinet-level federal agency, and turned it into the United States Postal Service, an independent federal agency with a specific mandate to “conduct affairs . . . on a business-like basis.”

Congress’s power under the Post Office Clause is consequential. It has been the source, supported by the Necessary and Proper Clause, of much federal criminal legislation. The Supreme Court has consistently interpreted this clause broadly. In Ex parte Jackson (1877), the Court held that congressional power over the mail is indeed far-reaching, including the right to determine what can and cannot be mailed:

The validity of legislation prescribing what should be carried, and its weight and form, and the charges to which it should be subjected, has never been questioned. . . . The power possessed by Congress embraces the regulation of the entire Postal System of the country. The right to designate what shall be carried necessarily involves the right to determine what shall be excluded.

In In re Rapier (1892), the Court held that Congress has exclusive jurisdiction over the mail, which includes the right to prohibit the circulation of materials that are immoral and injurious, such as lottery tickets. The Court in Brennan v. United States Postal Service (1978) reaffirmed the federal government’s monopoly over the postal system; and in United States Postal Service v. Council of Greenburgh Civic Ass’ns (1981), the Court upheld a federal law prohibiting the placing of unstamped mail in home mailboxes.

During World War I, the government’s power to ban incendiary and disloyal material figured largely in prosecutions under the Espionage Act of 1917. See Masses Publishing Co. v. Patten (1917). Later cases dealt with laws prohibiting the mailing of obscene material. Roth v. United States (1957); United States v. Reidel (1971). Meanwhile, lower courts added that regulations governing what materials could be mailed are subject to First Amendment scrutiny. See United States v. Handler (D. Md. 1974). The Supreme Court has confirmed that, like all other delegated powers, the post office power is subject to extrinsic restraints such as the First Amendment. For example, in Postal Service v. Council of Greenburgh Civic Ass’ns, the Court acknowledged the broad sweep of the Post Office Clause, all the while holding that its broad power cannot be exercised in a way that abridges the rights protected under the First Amendment. The Court has also held that the Tenth Amendment may also be a limitation on the postal power. Bond v. United States (2011).

Another area of contention relevant to the Post Office Clause is the franking privilege, which exempts all federal governmental officials from paying postage when conducting official business. The frank itself is a reproduction of the Member’s signature, which is affixed to the mailed item in lieu of a stamp. Members of the House of Commons and Members of the Continental Congress enjoyed the privilege. The First Congress retained the privilege in 1789. The Act of 1895, 28 Stat. 601, 622 § 85, restricted the use of the privilege only for correspondence on “official business,” to be interpreted by the Post Office Department, which would issue advisory opinions on whether a contemplated mailing could be franked. By 1971, after the Postal Reorganization Act, the Post Office had relinquished any responsibility to give advisory opinions. This led to a number of lawsuits by disgruntled candidates who ran against incumbent Members who used their franking privileges in mass mailings to constituents. Abuses became more flagrant, and the Franking Act of 1973, Pub. L. No. 93–191, 39 U.S.C. § 3210, was enacted to limit “official business” to “cover all matters which directly or indirectly pertain to the legislative process. . . .” The Act also laid out a noninclusive list of what constitutes official business, and established two special commissions, the House Commission on Congressional Mailing Standards and the Select Committee on Standards and Conduct of the Senate, to provide advisory opinions as to whether certain business is official or not.

The major controversy that raged over the post office power in the nineteenth century (following the Second Great Awakening) was whether Sunday deliveries ought to be discontinued in honor of the Sabbath. Congress had mandated seven-day delivery in 1810. Ultimately, the Sabbatarians failed. Sunday mail deliveries were too important to the people. The post office (usually in the general store) was usually the only place open on Sunday. It was the place to go to obtain the latest news (virtually all newspapers were delivered by mail), and to socialize around the issues of the day. In other words, the post office and its Sunday deliveries were too much of a civic association of the republic to give way to religious law. The federal government maintained Sunday deliveries until 1912.

The Postal Service has not fared well since the Reorganization Act of 1970. Competition from private carriers, the expansion of the internet, and a poorly constructed pension system have brought the agency near financial collapse. Because of its severe financial difficulties, both the Postal Service and proposed legislation contemplate ceasing most Saturday deliveries.