Prior to 1845, postage rates in the United States were excessively high. In addition, the rates were complex and difficult for the public to understand. The rates were not based on weight but on the number of sheets, including the cover sheet, in the letter. Personal correspondence was quite limited and there was very little business mail.

This situation brought about passage of the Act of March 3, 1845, effective July 1, 1845, whereby uniform postage rates were established. The basic provisions of the Act provided for the mailing of a letter for any distance of 300 miles or less, at 5¢ per half ounce, and for any distance over 300 miles, at 10¢ per half ounce. Drop letters for local delivery were to be charged 2¢.

This Act, however, did not authorize the Postmaster General to issue postage stamps in the above-mentioned denominations. This would not take place for two more years and the prepayment of the required postage would not be enforced until the mid 1850’s. The 1845 Act, however, did not prohibit local postmasters from issuing their own stamps for use on outgoing mail. This facilitation of prepaid mailing had the effect of increasing the postal receipts of the issuing postmaster, thereby raising his/her income.

These early stamps and stamped envelopes are known as postmasters’ provisionals. These were intended to be valid only at the post office where they were issued and were not to be accepted at other offices. These provisionals’ place in American philately is historically significant and the formation of a collection of these early primitives is considered to be one of the most challenging areas of advanced philately.