What is the rarest US quarter?

Certainly the single rarest US quarter is an 1866 proof version

• only one of these was struck, and it's impossible to put a value

on it.

The quarter with the highest market value is a 1795 Draped Bust variety with a small eagle on the back. As of 02/2011 a top-quality one is priced around $450,000.

Several other quarters fall in the $250,000-$550,000 range, including 1805 and 1873-CC.