What is the value of a 1921 Morgan Peace dollar?

There are Morgan dollars and there are Peace dollars from 1921, and they're not the same.

Morgan dollars have the familiar head of Miss Liberty and an eagle with outstretched wings on the back. These are worth about $15 in average condition, as of 07/2008.

Peace dollars have an eagle with folded wings and the Word PEACE on the back. These coins with a 1921 date are much scarcer than Morgans and sell for $85 to $150.