The mural is actually a petrachrome mosaic, drawn on 60 separate panels and colored with crushed stone in tinted mortar.
For 60 years the artwork stood mounted on a 14-inch thick concrete wall on Centinela and Florence, at the entrance of Centinela Park. Now, after painstaking restoration that took six years, it will grace another park: the Grevillea Art Park near Inglewood's City Hall.
Inglewood has a wonderful website devoted to the mural and its restoration, including a biography of Ms. Lundeberg, who died in 1999, and a detailed description of what petrachrome is and how it's done.
To see other pictures of the mural after restoration, check out the stories in the LA Times and LA Weekly. Pictures of "The History of Transportation" and other WPA artworks in Inglewood can be viewed at a website called WPAMurals.
Other examples of Helen Lundeberg's work are at her website (maintained by her estate). Finally, a list of WPA artworks in California, focused mostly on post offices, is here.