MDU Resources Group Inc is a construction and natural resources company operating in the United States. The construction operations, which generate the majority of revenue, provides construction and maintenance services, specializing in electric and communication lines, gas pipelines, fire suppression systems, and external lighting and traffic signals. The majority of construction customers are in the utilities, manufacturing, and governmental industries. The firm also has electricity generation, transmission, and distribution operations as well as natural gas pipeline, midstream, and distribution operations in Montana, North Dakota, South Dakota, Wyoming, Oregon, Idaho, and Washington.