Vulcanized rubber was invented in the 1830s, but before that, what was used to make the soles of a good, solid pair of boots? If a farmer or wanderer needed a good pair of work/hunting boots, what was used to make it durable? Layered leather? Wood? I imagine it changed from place to place as well.
Rubber soles only became common in the mid-20th century, long after the invention of vulcanized rubber you refer to. Indeed, the US Army was the first military in the world to adopt rubber soles when it did so in 1940. All other armies at that time used leather soles, often reinforced with steel hobnails.
For much of the 20th century and all of the 19th, leather soles were virtually all there was. Wooden soles have been used in places and at times, but they never seem to have been as popular as leather. They seem to have been less comfortable.