At night I exercised my memory by naming in succession the various firms.

Before long I could shut my eyes and, beginning at the foot of a business street, call off the names of the firms in proper order along one side to the top of the street, then crossing on the other side go down in regular order to the foot again.
The next step was to know the men themselves, for it gave a messenger a great advantage, and often saved a long journey, if he knew members or employees of firms.

He might meet one of these going direct to his office.

It was reckoned a great triumph among the boys to deliver a message upon the street.

And there was the additional satisfaction to the boy himself, that a great man (and most men are great to messengers), stopped upon the street in this way, seldom failed to note the boy and compliment him.
The Pittsburgh of 1850 was very different from what it has since become.