Leather was one of the critical industries of the Roman Empire. The imperial state provided contracts and subsidies to ensure that there was a sufficient quantity and quality of leather to keep legionnaires supplied with effective armor. As with most industries, leather production probably became more local during the third-century crisis. Although there was some fourth-century recovery, the military was meanwhile transitioning to depend increasingly on heavy cavalry in units that had adopted Germanic identities. So leather production was increasingly local or at best regional by the fifth century.

Once the imperial state broke down in the West in the late 400s, there was little infrastructure left to support major industries. This is especially true north of the Loire. Northern France and post-Roman Britain went into an especially dramatic material decline, apparently dominated by relatively autonomous villages. Elsewhere, aristocrats held on somewhat better, maintaining a greater sense of material difference from their social inferiors. In these places, and especially in the dwindling cities and at emerging ecclesiastical centers, leather production probably continued on a small scale.

Literacy is actually a fairly good measure of leather production, since vellum and leather are both made from working animal skins, through shaving, soaking, and shaping. Literacy became increasingly restricted in much of the old Western Roman Empire, and almost non-existent north of the Loire. I am familiar with only one facility capable of large-scale leather tanning in the British Isles during the early Anglo-Saxon period (500-800), and this was actually a vellum factory at a monastery in Scotland.

Things clearly start to change after 800. Charlemagne's empire was built on imperial estates, many of which could probably produce leather, and across the Channel in England, kings like Alfred the Great sponsored a revival of city life, which would also have led to increased leather production. At this point, leather would have again become fairly common, although I doubt whether a person could put together a suit of leather armor without the direct patronage of a king or estate owner.

I can't much speak to the rest of Europe or the later middle ages, but with regard to the early medieval West, non-aristocrats would have had very little access to tanned leather. They may have occasionally tanned or more likely tawed their own, but these poor-quality leathers have left little trace in texts or in the archaeological record. When non-aristocrats used animal skins, it was more likely in the form of untanned rawhide (just like a dog's chew toy), which is pliable when wet but brittle when dry. Rawhide can be very useful for lashing things together, but it's not flexible enough for use as clothing or armor.

I'm not aware of any major studies on leather in medieval Europe, and this has been my attempt to synthesize what I've read. There is, however, a very interesting book on leather in the early medieval Middle East, which might be worth a read:

• Patricia Crone, Meccan Trade and the Rise of Islam (2004).

I'm also very interested in this question. I sometimes get involved in discussions about the viability of leather as a material for armor and one argument is usually that it is much cheaper than something made from metal. I can not imagine that leather was a day to day material for peasants to have available.

I always assumed leather would be made by peasants themselves, and that at least low-quality leather suitable for bags or aprons would be made from butchered farm animals skin.

Am I wrong?