There's ruts all over the West.  The best/easiest location I know of is East of Independence Rock, WY.  It's still original grasslands there and three primary western trails converge.  Plus, Wyoming does a good job with their roadside notifications...

You can't really see the ruts in box canyon, but you can clearly see two places where they cut through the bedrock.  They cut it just wide enough for a single wagon to slip through, so the roadway was abandoned when the wagons got a little wider...

Thanks for stopping by, bozz.