On July 1, 1851 postage rates changed dramatically in the United States. The cost of letter mail dropped to 3c for up to 3,000 miles and 6 cents for further distances. This was later raised to 10 cents in 1855. 3 cent Adhesives and the new embossed envelopes made their appearance in Indian Nations mail. Also important was the 5 cent Penalty rate, imposed on unpaid letters; there were quite a few such letters from Indian Nations Post Offices during this period.
There are sub-pages by the alphabet for the Indian Nations Post Offices from or to which I have recorded cover scans during this period. Below is the complete list of the Post Offices: click on the post office name to be taken to the page containing the data for that office.