Alfred Abraham Gerngroß (1844–1908), who came from Forth near Nuremberg and had trained as a merchant at the Herzmansky company, founded a fabric store on September 26, 1879, with his younger brother Hugo (1857–1929) at Mariahilfer Straße 48, corner of Kirchengasse. After a brief competition with his former employer, August Herzmansky, the two companies attempted to collaborate, but this effort proved unsuccessful, leading to the dissolution of their partnership in 1881. Following subsequent success, the company gradually acquired 13 neighboring buildings. In 1883, the business was transformed into a partnership and grew into the largest department store in Vienna and, eventually, the largest department store in the Austro-Hungarian Empire.

From 1902 to 1904, Ferdinand Fellner and Hermann Helmer (the firm Fellner & Helmer) built a new five-story reinforced concrete structure on Mariahilfer Straße. The exterior facade was designed by Fellner’s son, Ferdinand III. The building featured five elevator systems and an escalator.
After the death of Alfred Gerngroß, the company was taken over by his sons Albert (1874–1972), Robert (1876–1942, died in the Holocaust), and Paul (1880–1954). On December 22, 1911, the company was converted into a joint-stock company under the name A. Gerngross A.=G. . At its peak, the department store employed about 1,600 staff. In 1926, the building was crowned with a lighthouse as a distinctive feature.

Source: Wikipedia