The item you are looking for is a painted container with various items of SWAG and a log book. Inside the lid is a code word necessary for completion of the challenge event.
This is one of the wider spots of the John Day river and one of the better bridges in the area. You will see significant haying activity in the area and not far from this location is a fish farm where many trout and sturgeon are grown for pond stocking. I think this bridge was named after the Stewart family who ranched nearby. Several years ago a Stewart passed away and left a very large estate to the county schools which has provided healthly scholarships to local youth headed for college.
Bridges are part of the highway system so be careful near this cache. There is safe parking near by but cars do move on down the highway. When I placed this cache there was haying going on down road but I don't know if the workers saw me placing the cache. I suspect these folks may be courious about the geocaching thing so maybe, if the opportunity presents itself, you can share the geocaching sport with folks.