A lot of hills here. A hard ride. Lots of erosion logs. Can be frustrating. There are 4 main trails. The first one starts near the parking area. That one leads to the second one which starts at the steps that you passed on the way into the park. This ends at a parking area where you can take a loop that brings you back around to there. The fourth one is out through the parking area across deer creek and follows the Susquehanna River back to where you parked.
Susquehanna State Park is located three miles northwest of Havre de Grace off Route 155 in Harford County. The park is approximately 35 miles north of Baltimore. Take I-95 north or south to Route 155, exit 89. Proceed west on Route 155 to Route 161. Turn right on Route 161 and then right on Rock Run Road. Follow Rock Run Road to the park.
http://www.singletracks.com/item.php?c=1&i=1068