As the U.S. Government was tiring of the costs to produce postals, the popularity of exposition and souvenir cards enticed more publishers into the business. Eager to transfer the burden of card production, but worried about the loss of revenue, the government issued new postal regulations but with many restrictions. Starting on July 1st, 1898 postcards could be sent through the mail for only one cent regardless of whether they contained a message or not. The Post Office Department also ended its monopoly on the printing of postals, but the words Private Mailing Card - Authorized by the Act of Congress on May 19th, 1898 were required to be printed on the back of all cards not issued by the government. Regulations also required that these cards be slightly smaller in size at 3 1/4 by 5 1/2 inches and printed in light colors of buff, cream, or gray. Many publishers could not afford to redesign their cards to meet the new regulations and they went out of business. But the lower price coupled with recovery from five years of depression brought an increasing demand for cards, which in turn brought a flurry of new publishers into the market. Some were waiting for the new regulations to take effect and had cards available that July. Larger images were introduced to the front of cards, though many mailing cards retained the format of the pioneers with a small illustration and a large blank area for writing.
While the many new postal restrictions prevented publishers from creating cards in the older pioneer styles there were many such cards out among the public when the Act took effect and these continued to be mailed. Since there were no penalties attached to the act, pioneer cards were either delivered or sent to the Dead Letter Office at the discretion of the mail handlers.
Use the link below for a more compleate history of this period.