Although the Depression years were technically 1929 to 1941, the term "Depression glass" refers to American-manufactured glassware produced from the early 1920s through the end of World War II.
Depression glass expert Gene Florence defined two distinct categories of this type of ware: "Elegant Glass" and "Depression Glass." "Elegant" glass was manufactured by a small number of companies known as "hand" houses, because they did a great deal of finishing work "by hand" after the piece was removed from the mold. Treatments would include fire polishing to remove "mold marks," grinding the bottoms so they would sit evenly, and acid-etching or cutting a pattern into the glass.
Companies who produced "Depression" glass usually left each piece the way it was when it came out of the mold. They performed little or no hand finishing work.
Many of the patterns were free "give aways" during rough economic times in the mid-1930s. To encourage customers, gas stations and movie houses gave out these items. Or you could find pieces in soap or cereal boxes. According to the National Depression Glass Association, one company was even saved from bankruptcy after receiving an order from Quaker Oats. They ordered so many pieces, the order filled five railroad cars!
In the first few decades of the 20th century, there were well over 100 glass companies in the United States. By the end of the Depression, only half remained. Some went out of business, but others were the victims of fire. During the 1930s, it was too difficult to recover from such a tragedy, so most factories were not rebuilt.
Depression glass comes in all kinds of colors, but the most popular were amber, yellow, pink, green, blue, and crystal (clear). Other colors -- such as tangerine and lavender -- were made in limited production, but did not sell well. As a result, they are more scarce and command higher prices than more common colors.
Depression glass is one of the most well researched and documented areas of antique collecting, so resources abound for those trying to identify pieces or learn more about the field. In addition to Gene Florence, other notable researchers include Marie Weatherman and Carl F. Luckey.