Anson Mills hired Henry C. Trost to build the concrete skyscraper facing you at 303 North Oregon Street. The building rises on the original site of the 1832 Ponce de León ranch, a layer of local history beneath its concrete frame. Anson Mills hired Henry C. Trost of the Trost and Trost firm to design and construct it; Trost was the area's foremost pioneer in the use of reinforced concrete.
Built in 1910–1911, this was only the second concrete-frame skyscraper in the United States and one of the largest all-concrete buildings of its day. At 145 feet (44 m) and 12 stories, the Mills Building was the tallest building in El Paso when it was completed. Trost and Trost moved their offices here on completion and remained until 1920; the Mills family later sold the building in 1965.
The building occupies a corner site opposite San Jacinto Plaza, its gracefully curved street facade wrapping around the south and east sides. Like many Trost designs, its overall form, strong verticality, ornamentation and cornice are reminiscent of the Chicago School work of Louis Sullivan. In 1974 the Mills Building's windows were replaced.
Notice the vertical lines rising to the cornice, echoes of Louis Sullivan's Chicago School, above San Jacinto Plaza.