Cunningham Drug Store was a chain, with locations including Georgetown Mall, E. Stadium Blvd at Washtenaw Ave, and in downtown Ann Arbor at the northwest corner of Main and Liberty. It operated the downtown location from 1940 until 1971.
The site was previously the location of Mack & Co., a department store that went out of business in 1935 during the Great Depression. The store's upper stories were removed and Cunningham Drug Store, a national chain, clad the first floor facade in glossy green enameled steel panels.
When Cunningham's closed, the space was briefly occupied by a plant store. In the spring of 1975, brothers John and Steve Gavas opened Parthenon Gyros Restaurant there. They removed the metal paneling on the exterior, exposing the brick wall of the former Mack store.
In 2012, the Gavas brothers sold the business to restaurateurs Greg Lobdell and Jon Carlson, who opened Lena. They restored the "Cunningham green" facade initially, but in late 2015 repainted it a dark blue.
Wikipedia: Cunningham Drug (U.S.)