From Wikipedia (so it HAS to be true)
Prior to the application of chrome in the 1920s, nickel was used. In the US for the short production run prior to the entry into the Second World War, plating was banned to save chromium and the decorative pieces were painted in a complementary color. In the last years of the Korean War, the banning of chrome was contemplated and several cheaper processes (such as plating with zinc and then coating with shiny plastic) were considered.
The largest plated parts were the bumpers of the cars. These were done by specialty shops, which had a different sequence of labor relations. Just after the Second World War, some American cars initially came off the assembly line with wooden bumpers -- not due to economy or rarity of the metal, but due to labor action at the plating shops. No doubt when the shops got on-line again these would be replaced.
Until the plant was shut down in the late 1990's, Cadillac's main manufacturing and assemply plant (located in Detroit, Michigan won awards for the best chrome plating line (including bumpers) in the world for over 50 consecutive years of operation.