People often assume that services which have been provided by government for decades or even centuries, are only provided by government because they CAN only be provided by government. They believe that the private sector would either not do as good a job or would price gouge the citizens.
Spooner proved this to be wrong. He created a company which was aimed to compete with the US postal service. His private and profitable company delivered mail to the entire country faster and for a lower price to the consumer. This was all while the US government had to cover the losses of the USPS with taxes.
At this point some people would question this statement. If it was true that Spooner had such a great system, surely it would still be the preferred mail company today!
But the US government saw that it was losing customers to Spooner's company. And even though it would have saved them money to just shut down the USPS and quit subsidizing it, they decided it would be better to ban all competition. This meant shutting down Spooner's operation, banning his innovative and productive contribution to society.
Today, these laws are still in effect.
There are companies like UPS, FedEx and DHL that would appear to be taking Lysander Spooner's place. But these companies are actually following the same laws which prohibited Spooner's business, but left a small exemption for parcels and expedient letters. They will deliver large overnight envelopes, but they will not deliver them standard ground mail or in a standard folded letter envelope.