In the 222 years since Benjamin Franklin first took the reins of the United States Postal Service, letters have been delivered to America's homes and businesses primarily via people, horses, and Jeeps.
But starting July 9, a modern icon of Americana - the minivan - will also begin carrying some of the 180 billion pieces of mail delivered each year.
In coming months, 9,000 Ford Windstars will replace a third of the service's familiar but aging fleet of some 27,000 Chrysler Jeeps, all of which will be phased out within five years.
But there's more to the switch than a hankering for new wheels.
The minivans are emblematic of a host of other changes at the Postal Service as the agency struggles mightily to keep pace in an era filled with e-mail, faxes, and hungry corporate competitors such as Federal Express and United Parcel Service.
The rugged Jeeps have puttered through America's neighborhoods since 1968 at a top speed of 35 m.p.h. They had small cargo areas. And in recent years they took too much time and money to keep operating. The Jeeps were perhaps symbolic of the public's perception of the Postal Service - slow, unreliable, and even ornery.
The minivans, which are to be formally introduced at a ceremony in Detroit, have much larger cargo bays - all the better to lug the growing mountains of J. Crew catalogs and direct and "junk" mail.
They also have big swinging rear doors and a low bumper for easy access - especially for the 55 percent of letter carriers who are women, and typically shorter than their male counterparts.
The new - and more genteel - postal workhorses also have air bags and antilock brakes (but, alas, no radios, which could be distracting, or air conditioning). The vans are being welcomed by some carriers who, while slightly nostalgic, say the cramped and clunky Jeeps are no match for bucket seats and left-side steering wheels.
"Some of them will miss the classic Jeeps," says Frank Santora, a program specialist in New Jersey, where the vans have been given a trial run in recent months. "There's going to be some nostalgia."
But ultimately the embattled federal agency can't afford nostalgia. At worst, disgruntled, gun-toting postal workers have become a standard late-night TV joke. At best, "lost in the mail" has become a euphemism for things that get bungled.
Across the country, corner post offices are being spruced up. And on-time delivery has improved. Customers will soon be offered a toll-free number to call about their mail. Spending on ads - including the new "supersonic" bald eagle logo - rose to $230 million last year. And the Postal Service is diving into new ventures on the Internet, such as creating secure electronic mail.
Many other changes have occurred outside the view of the general public. Among the service's billions of dollars worth of high-tech investments over the past decade are its automated letter readers.
"We have machines now that read the address, at a rate of 30,000 letters per hour," says Rod Sallay, a spokesman at the Postal Service's headquarters in Washington, and a former letter carrier.
If the machine can't make out an address, it takes a picture, which is read by clerks in North Carolina, who type a code that helps the automated machine send the letter on its correct path.
Some critics say, however, that the Postal Service isn't focused enough on customer service. For instance, it doesn't offer - as Federal Express and other competitors do - full-service tracking that allows customers to follow their package through the entire shipping process.
The Postal Service retorts that a new postal era is beginning.
Meanwhile, the Jeeps will be auctioned off, for $400 to $1,000. "I'm sure people are going to be lining up for the chance to buy those things," says Frank Santora, the New Jersey regional manager.