From 1753 to 1774, as he oversaw Britain’s colonial mail service, Benjamin Franklin improved a primitive courier system connecting the 13 fragmented colonies into a more efficient organization that sped deliveries between Philadelphia and New York City in a mere 33 hours. Franklin’s travels along the post roads would inspire his revolutionary vision for how a new nation could thrive independent of Britain. But not even he imagined the pivotal role that the post would play in creating the Republic.

By the early 1770s, Franklin’s fellow patriots had organized underground networks, the Committees of Correspondence and then the Constitutional Post, that enabled the founders to talk treason under the British radar. In 1775, before the Declaration of Independence was even signed, the Continental Congress turned the Constitutional Post into the Post Office of the United States, whose operations became the first—and for many citizens, the most consequential—function of the new government itself.

James Madison and others saw how the post could support this fledgling democracy by informing the electorate, and in 1792 devised a Robin Hood scheme whereby high-priced postage for letters, then sent mostly by businessmen and lawyers, subsidized the delivery of cheap, uncensored newspapers. This policy helped spark America’s lively, disputatious political culture and made it a communications superpower with remarkable speed. When Alexis de Tocqueville toured the young country, in 1831, the United States boasted twice as many post offices as Britain and five times as many as France. The astonished political philosopher wrote of hurtling through the Michigan frontier in a crude wagon simply called “the mail” and pausing at “huts” where the driver would toss down a bundle of newspapers and letters before hastening along his route. “We pursued our way at full gallop, leaving the inhabitants of the neighboring log houses to send for their share of the treasure.”

By the 1840s, though, the post faced a crisis. Average citizens, fed up with high prices—sending a letter more than 150 miles cost around 20 cents, or roughly $6 today—were turning to cheaper private carriers, almost putting the Post Office out of business. In response, Congress converted the post into a public service that no longer had to break even, and in 1845 slashed letter postage to 5 to ten cents, depending on distance.

The post continued to subsidize the nation’s transportation infrastructure. In the East, railroads replaced mounted couriers and stagecoaches. To connect the coasts, the department first financed steamships to carry the mail through the Isthmus of Panama. Then it invested in stagecoaches, which sped the mail from Missouri and Tennessee, where the railroads stopped, to California, enabling vital communications during the gold rush. In 1869, the great transcontinental railroad was completed. The mail was a lifeline connecting Western settlers with loved ones back home.

When the Civil War split America, Montgomery Blair, President Lincoln’s postmaster general, used the savings from suspending service in the Confederacy to upgrade the Union’s mail system. He expanded the Railway Mail Service, authorized the first money orders and began deliveries to urban residences, while the post became the first major institution to employ large numbers of women and African Americans.

The innovations that followed included Rural Free Delivery (1896) and Parcel Post (1913), which brought rural residents into the mainstream. At a time when banks largely ignored the needs of average citizens, the Postal Savings System (1911) provided basic financial services. As World War I engulfed Europe, the Post Office recognized the value of air transport and almost alone supported the aviation industry until the late 1920s.

The boom after World War II doubled the volume of mail even as the cash-starved department racked up big deficits and faced a fiscal crisis recalling that of the 1840s. Alarmed, Congress in 1970 remade the department into the United States Postal Service, a government-business hybrid that has received no tax dollars since 1982 but nonetheless remains subject to congressional oversight. By the end of 2006, the Postal Accountability and Enhancement Act had saddled the service with tens of billions of dollars of debt by requiring that it prefund its retirees’ health benefits.

While the post is once again the subject of controversy, it’s still the federal service that Americans rate most highly, according to a 2019 Gallup poll. Apparently unaware that much of the USPS’s business is now parcel delivery, which boosted revenue by $1.3 billion from 2018 to 2019, Jerry Seinfeld recently joked that he couldn’t fathom how a “system based on licking, walking and a random number of pennies” is struggling. Yet in 2020, with Americans isolated by Covid-19, countless folks depend on a system that supplies every address with critical materials, including stimulus checks, ballots and, perhaps soon, medical tests.