Walgreens, the largest US drugstore chain, is acquiring New York retailer Duane Reade for $1.1 billion, it has been announced. The purchase gives Deerfield, Illinois-based Walgreens a chain with the highest sales per square foot in the US drugstore business, while also strengthening its position in the north-eastern region that is the stronghold of its rival CVS. Walgreens currently has a relatively small presence in the New York City area, with only about 70 stores, 13 of them in Manhattan. By comparison, Duane Reed operates 257 drugstores in the same area.