What Is the 21st Wedding Anniversay Called?

Anniversaries up until the 15th have both traditional and modern wedding gifts associated with it. For example, the traditional 10th wedding anniversary gift in the U.S. is tin or aluminum and the modern gift is diamond jewelry. After the 15th anniversary, only certain years have traditional wedding gifts. The librarians at the Chicago Public Library included these years when constructing a modern gift list. For example, the 22nd anniversary gift is copper.