As Sam Calvert prepares to open one of the state’s first legal marijuana stores next month, he sometimes thinks of a historic parallel from a previous century. Washington may be about to experience a marijuana “Green Rush” similar to the Alaska Gold Rush at the end of the 19th century, when discovery of gold in the Klondike prompted thousands to seek their fortunes in unfamiliar territory. Only a small percentage of the miners who went into the frozen hills came out with enough gold to get rich, Calvert said. More people got rich by selling them picks, shovels and other supplies before they went in, and food and alcohol when they came out.