There are many places to purchase yarn, such as national chain craft stores or big box stores. Maybe you're looking for yarn that is a little more quality or locally made, however. Using a fine merino wool or yarn spun from alpaca is a different experience than using yarn made in a factory overseas. There are special places in right here in Spokane and Coeur d' Alene areas that sell specialty yarns.
These stores that have yarn, supplies and in some cases, classes. Most these stores sell over the internet, as well.
Another way to buy locally is to purchase online or at local art shops. Look for homespun yarn, once the farmer's market season starts again.
I'm also on Pinterest. www.pinterest.com/reinventspace/spokane-arts-crafts-examiner/