Conversation so far:
What kind of oil is in North Dakota
The oil-rich Bakken shale formation has made North Dakota the second-largest crude-producing state behind only Texas.
Why has the oil-rich Bakken Shale formation made North Dakota the second largest crude -producing state in the U.S.
North Dakota generated 852 million barrels of Bakken crude, The Bakken and the Three Forks formation are 94% of Dakota's current oil production, with about 1 million barrels a day.

Question: In how many U.S  states do we find the production
Self-contained rewrite: In how many U.S states do we find the production of crude oil.