From Stamps of the World
As a consequence of the compromise of 1867, the Empire of Austria postal administration was split between - what is called in English - Cisleithania and Transleithania, using different stamps and postmarks since 1871.
It is thus recommended to use more precise categories, like one of the Crownlands or provinces.
There were 3381 post offices at the Ausgleich time, reaching probably more than 10,000 before WWI.
This category has the following 28 subcategories, out of 28 total.