Manassas or Bull Run (Union battles are generally named after rivers while Confederate ones are after towns). Manassas is so named becase the Confederacy won there.
The problem with Manassas is that suburban D.C. has grown around it so it loses a bit of its charm.

Other alternatives (about 1 hr's drive NW of IAD) include Sharpsburg/Antietam Creek where the NPS has restored the place to what it looked like on the day of the battle, Gettysburg where the same is being done to (but it's a bit farther away) and the Wilderness (part of Fredericksburg and Spotsylvania) about 1 1/2 hrs S of IAD.

Go to the NPS site where you can use the search function for civil war sites.

NPS's Civil War site

[This message has been edited by terenz (edited 02-24-2001).]

[This message has been edited by terenz (edited 02-24-2001).]