Both college towns, Boston and Boulder, Colo., share another distinction: They lead the nation in marijuana use. Northwestern Iowa and southern Texas have the lowest use. For the first time, the government looked at the use of drugs, cigarettes, alcohol and various other substances, legal as well as illegal, by region rather than by state for a report Thursday. Regions could be as specific as Riverside, Calif., or as broad as all of the state of New York (minus New York City). Federal officials say the information will help states decide where they should spend money for treatment and prevention...