You can take I-95 to Fredericksburg, VA and then cut west on Rt. 17 to I-66 and then to I-81. That will bypass DC, Baltimore and Philly.
From I-81, take I-78 to I-287 and that will lead you back to I-95 and Stamford while bypassing NYC.
Campgrounds look sparse, especially ones that handle a 40 footer. Newburg, NY KOA (50+ miles) and Liberty RV Park (35 miles) seem to be your closest options unless a CT local knows of somewhere else.
Tom and Katharine
'07 Winnebago Tour 40TD, 400hp Cummins
RVing for 19 years & 150,000+ miles