Prior to 1863 there was no second "class" of mail as we know it today. Separate rates of postage existed for newspapers and magazines, and when additional printed matter was admitted to the mails it was charged the same rate as magazines. With the establishment of three classes of mail in 1863, newspapers and magazines came under second class rates, and other printed matter under third class.

Magazine postage was at first computed on the basis of "sheets." In 1845 and 1851 this sheet basis was changed to a weight or copy basis. Early newspapers usually consisted of one or two sheets and the rate was on a simple per copy basis. As newspapers became larger and more varied in dimension, size and weight became factors in computing postage. Distance was also a rate factor in the early years, but in 1852 was largely eliminated. The Act of 1852 also permitted magazines to move at newspaper rates for the first time—a forerunner of the combined (second) class for periodicals established in 1863. The flat rate (per pound or per copy regardless of distance) principle was continued in effect until zone rates for the advertising portions were established in 1918.

Collection of postage on newspapers and periodicals presented considerable difficulty during the early period. Prior to 1875, publishers were not required to prepay postage. As in colonial days, those who received newspapers had to pay one-quarter year's postage in advance. This policy prevailed, with some variations, until 1875, when prepayment of postage by the mailer was required.

Since 1879 the most important change in the second-class rate structure was the introduction of a distance factor in levying separate charges on the advertising portions of second-class matter. This change took place in 1918, the parcel post zones being used as the basis of a graduated schedule of rates. The rates for the editorial portions of publications have remained relatively stable in spite of the many changes that have taken place in both postal and publishing operations. The rates of postage for within-county mailings have not been altered since 1885, with the exception of a 1/8-cent minimum rate per copy ( excluding free-in-county mailings) which became effective in 1951. Eligibility for the second-class privilege has been redefined on several occasions in order to reduce administrative difficulties and help eliminate abuses of a subsidized service.

Transient second-class matter (mailings of second-class publications by other than the publisher or news agent) has been charged higher rates of postage than regular second-class mailings, and for a period of time was considered as third-class matter, as indicated in the tables.

Of all the areas of mail classification and postal rates, none has remained more controversial than that of magazines and newspapers. Over the years, changes in classification and rates have been attended with controversy as to what matter should be entitled to preferential second-class rates and how preferential the rates should be. Since 1918 this problem has been accentuated by the granting of special rate concessions to publications issued by certain nonprofit organizations.