Factory and General Offices H. Mueller Mfg. Co., Decatur, Ill. [Hold-to-light Postcard for the 1904 Louisiana Purchase Exposition (the St. Louis World's Fair)]

Decatur, Ill.: H. Mueller Mfg. Co., 1904. Very good. Undivided-back postcard; 3 1/2 x 5 1/2; mild age-toning and light wear to edges; in very good condition.From the Exhibit of Water, Gas, and Plumbing Goods at the Palace of Manufactures at the St. Louis World's Fair, the poscard showed the offices and the factory of the H. Mueller Mfg. Co. - founded in 1857 in Decatur, Illinois and known for gunsmithing, plumbing services, and sporting goods. The 1904 St. Louis World's Fair would be the place, where hold-to-light postcards would gain massive fame in the United States as popular souvenirs from the event. With die-cut windows and a hidden translucent layer between two card stock ones, when held up to a lamp or flame, the image magically transformed—windows "illuminated" at night, colors shifte, new hidden figures appeared, and the Moon and the Sun shone brightly.