Geo. Duncan & Sons (1874 - 1892) glass factory was founded in 1874 in Southside Pittsburgh and was a partnership of George Duncan, his two sons Harry B. and James E. Sr. and George's son in law Augustus H. Heisey.  Their signature patterns, known by some as "Early Duncan Glassware" include Ribbon, Three Face, Japanese, Shell & Tassel, Cottage, Ellrose, Zippered Block, Gonterman, and Snail, but there were many more.
      In 1891, the factory joined the U. S. Glass Co. combine as Factory "D".  The following year, the factory's main building burned down & apparently some of the molds survived or had already been moved to other plants incl.to Doyle & Co..
      James, Sr. who was initially the supervisor of Factory D, had left the US Glass Co. in November of 1891.  In 1893, after the 1892 fire, James, his brother Harry & John Ernest Miller, who had been supervisor of the Pittsburgh Duncan factory mold shop, opened their own factory in Washington, PA, about a half hour south of Pittsburgh, forming a new partnership
George Duncan's Sons & Co. which has also been known as Geo. A. Duncan & Sons (1893 - 1900). Some of their patterns were: Flowered Scroll, Duncan Flute, Zipper Slash, Grated Diamond & Sunburst, Paneled Diamond Block, Quartered Block, Diamond Block Band, Tepee, Scalloped Six-Point, Button Arches, Bassettown, Mardi Gras, Button Panels & Starred Loop.
      After James died in 1900, John Ernest Miller became a full partner and the factory became Duncan & Miller (1900 - 1955).  Their patterns include: Diamond Ridge, Block & Rosette, Ladder with Diamonds, Colonial, Thumbprint Block Band, Clover, Homestead, Sunburst in Oval, and King Arthur
      Augustus Heisey, who owned the other half of Geo. Duncan & Sons (through his wife, Susan Duncan) stayed with US Glass until he left to form Heisey Glass Co. in the mid-1890s.

     The relationship between these companies has caused a lot of confusion through the years, but the only connection was the involvement of some of the same people. Other than the name, the connection between the original Geo. Duncan & Sons factory and the one that became Duncan & Miller is exactly the same connection that exists between the original company and Heisey Glass Co. It can be confusing -- after all, both factories had similar names, and that wasn't by accident -- when James Duncan started up the Washington factory, he wanted people to know that he already had extensive experience in the glass business. Some of the early ads make it look like the Washington factory was indeed just a continuation of the Pittsburgh business. But there was no sharing of patterns, something that earlier glass writers didn't always understand. Heacock attributed some of the Washington patterns to US Glass as a result of the confusion; although he corrected the error later, you still find it perpetuated in some books.