In 1967 the coal and lignite resources of Wyoming, North Dakota, and Montana were estimated at 1,455 billion tons, which amounted to 45 percent of the weight of the solid fuel resources of the United States. Lignite in North Dakota constitutes about one-third of this reserve and would be more conservatively estimated at 350 billion tons. Lignite production in North Dakota in fiscal year 1971 amounted to 5.8 million tons, which is more than double the production in 1965. By 1976 it is conservatively estimated that production will exceed 10 million tons. Currently, most of the lignite has been used for electric power production.