Nothing within an hour, more like 2 hours or more to real trails. If you do go to Peters Mill, definitely take the scenic route described at the bottom of the page link above. Nice drive, and might actually be quicker.
However, there is an area between DC and Baltimore that I think you would enjoy.
Pictures of the area Shoot me an email and we'll see if we can't give you a tour.
Brent
[ 11-21-2001: Message edited by: OffroadX ]