We live in a society that is constantly changing. The way we dress ourselves is one such way. Through the changing images of Madonna one can see the fashion changes in American popular culture throughout the last twenty years.
America is a capitalist society based on big corporations seeking a profit off of us, the consumers. Installed in us through social conditioning (such as TV, kids at school, and most notably our parents), is the want to keep "up" with what's considered "in" and discard what is "out". One such example would be how everyone wants new cars, because "newer is better" even though the car you own may be perfectly fine. This is known as materialism.
Madonna is notoriously known as "The Material Girl" to many, as she has always kept "up" with the newest fashion. The changing images illustrate these changes in Amrican culture. By keeping "up" with them, Madonna has stayed "in" as a celebrity and has claimed her spot as a celebrity icon.