The cache is not at the posted coordinates, however it might be a good place to see a champion Bur Oak tree while you are here for the bonus.
After your completion of the Adventure Lab Cache:
The Underground Railroad in Harford County
Use the information you obtain at each site as you answer the Adventure Lab questions and write down the values of A through E. The cache can be found using this information to complete the following:
N 39 36.ABC W 076 08.DEB
Using the final coordinates for GZ, subtract 0.010 from the latitude and subtract 0.020 from the longitude to find an opening in the stone wall to go into the woods.
Placed with permission from the Steppingstone Farm Museum. Please be mindful of the hours the grounds are available. The grounds open from roughly 9:00 AM to sunset daily.