BISMARCK, N.D. (AP) — Real-world research in more than a dozen states in recent years is giving farmers new understanding of how to grow industrial hemp and showing that it has promise to be a viable commercial crop in the U.S.

The 2014 federal farm bill allowed for university and state-sponsored research programs of the plant whose fiber can be used in products from paper to clothing and whose oil can be an ingredient in food and health products. Programs have now been launched in 15 states, with two more states coming online, according to the hemp advocacy nonprofit Vote Hemp.

"These last se...