Used as we are to the modern megalopolis, we might at first think that Luther’s Erfurt, home to some 20,000 people at the time, was a country backwater. This was not the case.
Precise population figures about the era are hard to come by, but in 1500 even Europe’s most populous cities paled in comparison to the great metropoli of the rest of the world. Before its encounter with Spanish troops, for example, Tenochtitlan is conservatively estimated to have housed half a million people, two to three times larger than Europe’s largest.
No, Europe was small potatoes in 1510. Rome, the former behemoth boasting over a million residents in the late-classical era, had shrunk some 2000% to around 40,000; all of them and more could have fit into the Colosseum. By the time Luther arrived in 1510-11, sheep had been grazing within the old walls for a millennium. Geneva, for all its later importance, was less than 5,000. Northern cities like Paris, London, and Rotterdam were at the head of the pack with populations between 100,000 and 200,000. Cologne and Nuremberg, the largest cities of the Holy Roman Empire, topped out around 40,000 in 1500; Strasbourg was a bit smaller at 25,000. So at 20,000 inhabitants Erfurt could consider itself one of the more important cities in Germany.
Like other urban centers, Erfurt’s life was based on being a center for the distribution of agricultural surplus. Towns are in their origins actually markets, and Erfurt utilized this bustling agricultural commerce to build several large churches and monasteries, a university, and a nascent printing industry. It was also known for the quality of its blue dye, derived from the roots of the woad plant. It was Luther’s next post, Wittenberg, with its mere 400 houses, that was the backwater—not Erfurt.