The rise in popularity of picture post cards was a direct result of the passage of the Act of May 19, 1898. This act allowed for private mailing cards to be transmitted through the mails at the same rate as government postal cards, as long as they were the same general size and weight and conformed to the same regulations as the government postal cards.

Prior to 1898, private mailing cards were sent at the current letter rate. Cards were not readily available, and were many times homemade or imported from Europe. There are some exceptions, however , all of which are desirable and highly sought-after by both the deltiologist and the postal historian. Most picture cards were simply the printed backs of the government cards, most notable being the various Expositions cards and particularly the Columbian Exposition Cards of 1893.

The post card craze is usually defined as lasting from about 1900 to about 1920, with the period of about 1902 to 1913 being the peak of the "craze". There are several types of post cards that existed during this period.

The first of these types was the Private Mailing Card. These cards were printed for a short period starting in 1898. They began the period when many private manufacturers started printing cards. These are identified by the words "Private Mailing Card" or imprinted "Authorized by an Act of Congress May 19, 1898" on the back side of the card. A number of enterprises also took advantage of the act to print cards other than picture cards for business purposes, but soon found that the standard government card was cheaper and not as labor intensive.

Many collectors refer to private mailing cards and the type of post cards that came just after as "undivided backs"; these are simply cards that were only allowed to have the address only on the back of the card and had no dividing lines on the backs of them. Only the address the card was sent to was allowed. No return address or message was to be written on the back according to the law.

In 1907, the U.S. Post Office finally allowed for divided back cards, while many of the major European countries had allowed divided backs since 1902. Many cards with divided backs are found from the period of 1902 to 1907. This is because many of the high-quality cards were imported from Great Britain and Germany, one of the most famous companies being Rafael Tuck and Sons, who had been importing cards to the U.S. since 1899. These divided back cards were produced until about 1920, when the "white border" cards came into existence.

People not only started mailing post cards, they started collecting them. It became, in the nomenclature of the day, a "craze", much like the beanie babies of today. At the start of World War 1, when the country's attention turned to more important matters, Germany became the enemy and Great Britain went to war, vastly reducing the availability of picture post cards. The post card craze started dropping off. It was kept barely alive by the soldiers sending home picture post cards from overseas. Cards from France and Belgium, and to some extent Great Britain and Germany, are often found in old collections. By 1920 the post card craze had settled into more conventional use, much like we use post cards today.

Even today, large old post card albums turn up. Every trip across the county or to the nearest vacation area was represented with post cards. Post cards were sent offering greetings for birthdays, Thanksgiving, Easter, even Saint Patrick's Day, Independence Day, Halloween, and especially Christmas and New Years. Cards were produced to commemorate train wrecks and natural disasters, airplanes and automobiles, famous buildings, train stations and everything in between! Kodak even produced the post card camera and so a person could produce their own images for post cards!

Post cards became a major advertising force during this period, featuring images for every product you could imagine. In the days prior to commercial radio and televison, it was the mass advertising medium of choice. Many of these cards advertised beer and liquor, food, medicines and more. They are some of the most highly-valued and sought-after post cards today. The second World War and the advent of commercial radio slowed the flood of advertising cards, adding to the decline of the post card craze.

Many of our grandparents and great-grandparents had post card parties to show off their albums and newly-acquired cards. Post card albums were found in nearly every parlor, and all visitors were expected to view them, usually before dinner parties or other events, much like our family photo albums are today.