During America’s dry age, the federal alcohol ban carved out an exemption for medicinal use, and doctors nationwide suddenly discovered they could bolster their incomes by writing liquor prescriptions. Pharmacies, which filled those prescriptions, and were one of the few places whiskey could be bought legally, raked it in. Through the 1920s, the number of Walgreens stores soared from 20 to nearly 400.  Read more at the NYT