Confederate States philately has always enjoyed enormous popularity. The stamps are interestingly printed, served a real postal purpose, and the story behind the stamps has real philatelic appeal- large nation, rent by discord, one section withdraws from union to preserve the ability to own human beings as property, the other side fights to retain the union and end slavery. If it wasn't true it would seem unbelievable.
Losers in wars and political conflict tend to gravitate to the stamps and postal history of their side as a way to identify with their cause and ameliorate their sense of loss. Baltic States philately between WWI and WWII, when these countries had been absorbed by the Soviet Union, is a case in point. Confederate States philately has always enjoyed great popularity in the south as kind of rebellion by proxy- collecting those stamps gave old time Confederate collectors succor for their sense of loss of what they called their old life and their peculiar institution.
The stamps of the Confederate States have always been highly specialized in and have attracted some of the finest American philatelists. A fine catalog, by August Dietz, was issued fifty years ago. A wonderful reissue and expansion of this catalog has just been published by the Confederate Stamp Alliance (note the deliberate acronym- CSA- if you doubt the thesis that philatelists carry on the old fights symbolically through their collecting). It is rare that I recommend a $125 specialized catalog. With fascinating information about the stamps and postal history of this important period, along with accurate pricing, this catalog is a gem.