Many people think of sourdough as something from the Gold Rush days. Sourdough was the first way raised breads were made. There are a number of recipes for sourdough starter, but this is one I've used, and it works fairly well. It came originally from the cookbook The Complete Sourdough Cookbook by Don Holm.
Procedure Get a container for the starter.
Try to get something with a lid. I use a vinyl plastic food-storage container. Notes If you do a lot of bread baking, there will probably be enough yeast spores floating around your kitchen so that the added yeast isn't needed. If the starter starts turning orange or green, throw it away. After the starter is ready, it can be used immediately.