Oregon marijuana shops opened their doors Thursday to recreational users for the first time. Some of the more than 300 marijuana dispensaries across the state stayed open until midnight to mark the occasion, selling to adults 21 and older. The sales will be tax-free until January, when a 25 percent state tariff goes into effect. Customers can buy as much as seven grams at a time of dried marijuana flowers and leaves along with plants and seeds. Oregon joins Washington and Colorado as the only states where pot can be sold for recreational use. Voters in Alaska and the District of Columbia approved recreational marijuana, but sales there have yet to begin.