A building that architectural critic Ada Louise Huxtable once called a “post-war miracle” could soon vanish from the streets of Manhattan. And if 270 Park comes down, so will a key part of the legacy of pioneering female architect Natalie de Blois. De Blois, who joined the renowned architecture firm Skidmore, Owings & Merrill (SOM) in 1944 and passed away in 2013, helped design headquarters for the Lever Brothers, Pepsi-Cola, and Union Carbide. The Union Carbide office, located on Park Avenu…