Why is the 25th wedding anniversary called the silver wedding anniversary?

This occasion was traditionally celebrated privately by married couples for a good 25 years of marriage. The norms followed by the man was to crown his "queen" with a silver, jeweled wreath as a symbolic object of love, respect, and approval. Hence, the name. Also, if the married couple reaches 50 years of togetherness, the man is to crown her wife with a golden wreath.