Peppermint (Mentha piperita) is the second most popular essential oil in the United States. It is cooling to the skin and gives off a fresh, grassy aroma. This U.S.-sourced essential oil comes from the prominent Yakima valley in Washington state. Peppermint is believed to be native to the Mediterranean region, although the actual origin is uncertain. The crossing of its two parent species — mentha and pepita — occurred in the wild.