In “The Wealth of Nations” (1776), Scottish economist Adam Smith declared that a postal service is “perhaps the only mercantile project which has been successfully managed by, I believe, every sort of government.” Like a sound currency, an efficient civil service and a transportation network, it had become requisite for nationhood.

At this very time, Winifred Gallagher reminds us, the American colonists were using a rudimentary communications network to develop a new, independent-minded, unified and increasingly democratic culture. In “How the Post Office Created America,” Gallagher (whose books include “House Thinking,” “Just the Way You Are” and “New: Understanding Our Need for Novelty and Change”) provides an engaging and informative history of the service over the ensuing 2½ centuries.

A “natural monopoly” established, regulated and run by the federal government, the post office, she demonstrates, is one of the greatest — and least appreciated — American institutions.

The Post Office Act of 1792, Gallagher explains, authorized mail service for the entire population, including those living in remote areas. The legislation sidestepped states’ rights debates by empowering Congress to establish postal “routes” rather than “roads” (which were seen as a prerogative of the states).

By reducing or eliminating postage fees for newspapers, Congress helped foster a robust civic and political culture in the United States. And, Gallagher indicates, a host of initiatives — including free home delivery, rural free delivery, railway mail service, parcel post, postal savings banks and airmail — made the U.S. Postal Service the envy of the world, in price and efficiency.

Gallagher acknowledges that officials of the Postal Service did not anticipate the digital revolution. They didn’t take the lead in providing Americans with inexpensive, secure broadband access and e-mail accounts, or repurpose post offices as neighborhood media hubs equipped with computers as an extension of universal service.

That said, she makes a compelling case that Congress shares the blame for the Postal Service’s current woes. In recent years, she points out, legislators have imposed significant financial burdens, capped rate increases below the Consumer Price Index and obstructed efforts to modernize or shut down post offices.

Most important, she argues that it is a mistake to view the Postal Service as a business, driven by the market and supported by its customers, instead of an essential public service. Given the need to serve people who live in sparsely populated parts of the country, she says, privatization would be an even greater mistake.

For all its problems, Gallagher concludes, the U.S. Postal Service remains the world’s most productive postal system. Making visits to more than 154 million addresses almost every day, it continues to be a bulwark of our democracy.

 Glenn C. Altschuler is the Thomas and Dorothy Litwin Professor of American Studies at Cornell University.

How the Post Office Created America
By: Winifred Gallagher.
Publisher: Penguin Press, 326 pages, $28.