Horizon Organic is an American company which produces organic milk products. It is the largest supplier of organic milk in the United States. Horizon Organic was founded in Boulder, Colorado in 1991. It began selling its products nationwide in 1994. In 1999, Horizon Organic expanded into the United Kingdom when it took over the British company Rachel's Organic. The Horizon Organic brand is now owned by WhiteWave Foods, formerly a division of Dean Foods, of Boulder, Colorado.