The track seems to be operating as of 2022. From Facebook page: 1/3rd Mile Natural Clay Track, owned by private family, located in Greenland, MI., in Michigan's Western UP County of Ontonagon. 15 miles from Ontonagon, 40 miles from Houghton. There is an article here about the track.
This track has previously operated under the name Venture Raceway. Also Adventure Mountain Speedway.