Sourdough has been made since ancient times; it dates back to Ancient Egypt around 1500 BC. In Europe it has been used as the main kind of bread until they developed a way to cultivate yeast in the Middle Ages. Rye bread is still popular in Europe and since baker's yeast is not really useful for leavening rye bread the sourdough method is still used.
Sourdough also has a history in the US during the California Gold Rush it was used as the main kind of bread because it was more reliable than other kinds of bread and could last for longer periods of time. One of the most famous exports in the US is the San Francisco sourdough which is very popular to this very day.
It has been made for over 150 years and has become popular due to its fine taste with seafood and soups alike. Today sourdough is not very popular, it takes too long to make but some restaurants keep it on their menus.
There are many kinds of sourdough but most are made the same way, one exception is the Amish Friendship Bread which is not sour due to the presence of milk and sugar in the recipe. While sourdough is not the most efficient kind of bread and it might not be the best tasting, it has something unique to it and shows the way nature works, it does not rush anything and it does not try to do more than its possible, yet everything that's important gets done.
Source by Antonio Musa