http://www.gonorthwest.com/Washington/northeast/Dry_Falls.htm

As the name suggests, Dry Falls no longer carries water, but is
the remnant of what was once the largest waterfall known to have existed on
earth. Viewing the 3.5 miles of sheer cliffs that drop 400 feet, it is easy to
imagine the roar of water pouring over them. (Niagara Falls by comparison, is
one mile wide with a drop of 165 feet).

Thanks to Jeff Kohler.