The Walla Walla area needs a few more letterbox hybrids, so here is one to add to your count. You will find that the cache name corresponds to the stamp that is inside of it. DO NOT TAKE THE STAMP! It is NOT a trading item. It needs to stay in the cache container. Also, the container DOES NOT have a stamp pad or a pen in it, so you will need to supply your own.
Keep in mind, your cache name/letterbox stamp needs to be on the cache log to count it as a find!
Have fun!