Lance Creek oil and gas field, discovered in 1918, is on a large anticline. Structure has controlled the accumulation of oil and gas. Production is from sands of the Dakota group (Cretaceous). The First, or Muddy, sand yields oil in small amount in a limited area on the crest of the fold, but the principal production is from the lower sands of the Dakota group. In these sands, gas in large volume is found throughout a large area, and a very narrow strip of oil territory borders the gas cap on the south and east. Because of steeper dip, the oil-bearing zone in these sands is probably much narrower on the north and west flanks than on the others, and has not yet been found by drilling, though there seems no reason to expect it to be absent. The water table originally plunge eastward, and production was obtained at the east end of the field down as far as the limit of closure, but farther west production was never found so low structurally. The gravity of the oil is 41.8° Be. The average recovery of gasoline from the natural gas is 1.54 gallons per thousand cubic feet. To January, 1927, the field had produced nearly 3,500,000 barrels of oil.