Mortimer Building, 159 Fifth Avenue (935-939 Broadway), ca. 1977.

Completed in 1862, The Mortimer Building was an early exemplar of the commercial architecture that would transform today's lower Flatiron District during and immediately after the Civil War.

The Italianate-style department store, owned by the developer and stockbroker Richard Mortimer, is attributed to the prolific architect Griffith Thomas, whose later works include several cast iron-fronted loft buildings included in the SoHo Cast Iron Historic District.

In its Ladies' Mile Historic District Designation Report (1989), the Landmarks Preservation Commission acknowledges the influence of the earlier, J.B. Snook-designed A.T. Stewart department store at Broadway and Chambers Street. In the immediate post-war period, department stores like Stewart's and Lord & Taylor began to open "uptown" outposts near Madison Square.

The brownstone Mortimer building, with frontage on Broadway, Fifth Avenue, and East 22nd Street, blends with the area's previous residential architecture, while looking toward the neighborhood's future as a commercial district. Indeed, Mortimer's building was home to the very first offices of the American Institute of Architects, founded in 1866. Early commercial tenants included a variety of retail merchants (it's now a Restoration Hardware showroom). Apart from small changes to storefront window displays and cornice alterations, Thomas's design remains largely intact.