Very Slim Pickings in Baltimore County
Morris Meadows in Freeland (off I-83 near PA line) is the only one I know of in Baltimore County.
Ramblin Pines is in Woodbine, Howard County (West of Baltimore, Near I-70 and MD 97)
Capitol KOA in Millersville, AA County (South of Baltimore, Near I-97 and MD32)
Bar Harbor RV Park in Abingdon, Harford County (Northeast, Off I-95)
That pretty well covers the Baltimore Metro Area. The Millersville KOA is only one I've stayed at. Nice, but some sites are small in the wooded areas.
2004 Dodge Ram 2500 Club Cab 4x4 CTD
2007 Sunline Solaris T-276-SR: Misty Blue/Cherry
2001 Dodge Ram 1500 Reg Cab 4x4 OFF-ROAD