This pattern was designed by Phillip Ebeling who also designed Fostoria's American pattern.
According to Volume III, of Measell's "Imperial Glass Encyclopedia" this pattern was first produced in the early 1920s and called Prism. Later it is found in a 1920s era Imperial catalogue and identified as Triangle. In the 1930s, the name transitioned to Mount Vernon. It was during this era that the pattern became one of Imperial's best sellers ranking only second to Cape Cod. In 1940, the name was again changed to Washington. It is believed this was due to a conflict with the Cambridge Glass Company over using the same name as their Mount Vernon pattern.
