What U.S. government institution, short of Congress or the Executive Branch, has it's history dating all the way back to the Constitutional Convention of 1789? The U.S. Postal Service, of course. Based on the policy then established, Congress passed the Post Office Act of 1792, establishing the position of Postmaster General, setting initial postal rates and outlining postal rules and regulations. By 1851, post offices had expanded from 75 up to 18,000 - one post office for every 1,250 people. You had to pay for your mail and pick it up back then, but post offices became a core community hub. Most were classified as 4th class post offices, often located in a community general store.

Since the Postal Service was granted a monopoly by congress, having one located inside your store could be a real boon to business. And since the Postal Service, with lots of "help" from local congressmen, also established the location of Post Roads, their political sway could be significant. Urban post offices, like those in New York, grew to be very large and limited in the number of post office boxes available. Crowding thus gave rise to pick pockets and "penny posts". People seeking to have their mail delivered to them, avoiding the chaos, paid a penny delivery fee to enterprising "mailmen".
In response, seeking to protect their mail monopoly, congress authorized free home delivery in cities with 10,000 or more people. Not to be left out, rural populations clamored for service. After all, in 1890, 75% of the U.S. population lived in rural areas not covered by free delivery service. Again, congress responded and Rural Free Delivery (RFD) came into being followed by the addition of free Parcel Post service in 1913.
One wagon design appears to have been used across the country when mail carrier routes were too long for delivery on foot.

Here's a mail delivery wagon in Redmond in 1910.

Image courtesy University of Washington Libraries, L 83.92.12, circa 1910
Railroads also played a big role in the USPS country wide mail and parcel post delivery system. The following photo of a Great Northern Railroad mail car leaving Seattle shows men sorting mail in post office rail car

Image courtesy University of Washington Libraries, P125087, Seattle Post Intelligencer photographer, circa 1944
"The United States Government introduced railway post office cars in 1862. As the train sped along the tracks, postal workers sorted letters and packages for all of the towns along the route. Trains carried most of the nation's intercity mail until the 1970s."
If you want to make big money, being employed by the USPS would not be the path to riches. This photo from 1955 tells the story.

Image courtesy University of Washington Libraries, 1986.5.11150, Seattle Post Intelligencer photo, circa 1955
The postal workers shown above are celebrating having just won a big raise after several years of drought. Any guesses as to how much of a raise? 8.1%. Sounds good, right? Perhaps not so good, when your hourly rate goes from $1.61 to $1.81/hr. and your annual increase totals all of $300. Even in the 1950's, that wasn't much. I think I made more than that in the bulb fields.
Over the years, the number of post offices have declined significantly.

Fast forward to today and we see a whole lot of change in communications - the digital age. Mail volumes have fallen dramatically. On the other hand, home parcel delivery is on the upswing, further boosted by todays coronavirus pandemic. Change however, has not been uniform through the years and there remain big gaps between those living in rural vs urban areas.
- Today, 14.5 million people in rural areas lack access to broadband
- 18% of americans still pay bills by mail
- A significant percentage of rural residents vote by mail
- USPS delivery service is the only delivery service available to many rural areas
- What business will want to provide service and lose money
Should mail and parcel delivery service really be dropped for so many? Or charge rural customers higher rates that city slickers?