If there are any travelers going through Montana to the National, or just cruising through this summer, we do have a farm just south of Laurel, outside of Billings, that you are welcome to park for a night or two. Boondocking is best, but there is some electricity and water outside the barn. We are two miles south of Laurel, on the road to Yellowstone Park.
We have a farmers market here, and river frontage if you care to share the field with cattle. Or stay up by the barn which is more civilized, right off the highway. Lots of in season veggies, and free parking. (May cost you a beer if it's hot and I am actually working that day).
We are Greg and Leslyn. Just look for the trailer painted like a pumpkin in the field with a large red barn (No, the pumpkin trailer is not our airstream). Pull in and say howdy, and stay awhile if you want.