From the west on US Alt 40, take MD 67 south for 7 miles to Gapland Road/MD 572. Go left(east) on Gapland 1 mile to Gathland State Park in Crampton Gap. The most prominent feature in the park is a stone arch at the intersection of Gapland Road and Arnoldtown Road. Alternatively, from the east on US 40A, take MD 17 south from Middletown for 6 miles. Turn right(west) onto Gapland Road/West Main St in the small town of Burkittsville and go about a mile to the park.
You can use this address to find the parking lot:
Gathland Trail Start, 1005-1037 Arnoldtown Rd, Jefferson, MD 21755
I sleep at trailheads, and this is a fairly busy one. Because of the short ascent up the appalachian trail (follow the signs by the ruins of the barn behind the parking lot), it is a very easy hike-in to shelters and a designated camping area.
The shelter is northbound on the AT not even a half mile, on a spur trail. You can't miss it! The shelter is big (look up "crampton gap shelter"), and if you have a tent, you can just use your tent in any of the designated sites.
Or you can be like me. I didn't want to sleep in the car, so I just hiked up to the shelter and camping area and it was crowded. So, i just threw my bivy bag anywhere in the leaves fairly level and that was that.