Waulsortian-type carbonate mud mounds in the lower Mississippian Lodgepole formation (Bottineau interval, Madison Group) comprise an important new oil play in the Williston basin with strong regional potential. The play is typified by wells capable of producing 1000–2500 bbl of oil per day and by reserves that have as much as 0.5-3.0 million bbl of oil per well. Currently centered in Stark County, North Dakota, along the southern flank of the basin, the play includes 38 wells, with 21 producers and 6 new fields. Initial discovery was made at a Silurian test in Dickinson field, traditionally productive from Pennsylvanian sands. The largest pool discovered to date is Eland field, which has 15 producers and estimated total reserves of 12–15 million bbl. This report summarizes geologic, well-log, seismic, and production data for this play, which promises to expand considerably in the years to come.