The reasoning behind this issue
On the occasion of the 400th anniversary of the Landing of Columbus the largest Exposition ever held on US soil was held in Chicago. The Post Office was determined not to miss out on this and proposed a series of stamps to commemorate the event. The purpose behind this was three fold

1) To encourage the purchase of stamps by the public
2) To stimulate the hobby of stamp collecting
3) To make a tidy profit

Production and Distribution

It was estimated that 3 Billion stamps would be sold and between September and the end of December 1892 work progressed on their production.

The Post Office Dept. informed all post offices that they would not be able to order the new series on an 'as needed' basis as was the normal procedure. Instead they would be sent an amount the powers to be deemed sufficient. Plus the department would not accept any returns and they would not be issued any other stamps until they had run out the new series. This caused much complaining by the post office owners, complaints were coming in that these stamps were too big, being twice the size of current issue (this was done to accommodate the expansive designs).

At the Exposition

At the Exposition the Post Office was in the US Government Building and had been given a vast amount of display space. The display cases showcased stamps from the very earliest days of stamps to 1892 both in the US and around the world. Postal cards were sold in every building and of course one could purchase the new Columbian series stamps.

Popular then not so much
At the Exposition
The post offices need not have worried. The stamps proved to be immensely popular. So much so that Post Offices refused to sell the higher values for fear of running out. The price of these skyrocketed as a result. Companies instructed their offices to use the higher values on internal parcels so they could benefit from their sale when delivered to their branch offices. US travellers in Europe were accosted for them, they were even traded on bourses.

And then like all bubbles, it collapsed. Before you knew it the $5 stamps were being sold at a steep discount. Being totally useless for letters, and with a world glut the price dropped like a stone, at one point stamp dealers would only offer 30% of the face value for them.