Ensign United States Drilling serves oil and gas companies active in exploring and producing in the US by providing equipment and services for drilling oil and gas wells. It is a subsidiary of Ensign Energy Services which provides contract drilling services primarily in the Rocky Mountain region, California, and the southern US. It claims to be the second-largest and most active land-based drilling contractor in the Rockies. Ensign United States Drilling has 56 drilling rigs in operation in the Rockies and in Michigan, Nebraska, North Dakota, South Dakota, and Pennsylvania. The company, in concert with sister companies Ensign United States Drilling (California) Inc., and Ensign US Southern Drilling LLC, make Ensign Energy Services one of the largest land-based drilling contractors in the US.