We stayed at Harold Parker State Forest in Andover, MA (NE of Boston). It was a very nice state park with lots of trees and nice sites but the 1-way roads are very narrow to get into some of the sites (we ended up pulling in and then turning around in the site). If you can try sites 222 or 223. There are no hookups. We stayed there 9 nights and the solar panel on our Sunline kept the batteries well charged, even through 4 days of rain. The rangers were very helpful and had maps of how to get to the T (Oak Grove) which we used to go into Boston.
We got a 2-day Go Boston pass (through the internet but don't know the site) that was very useful. Also bought a pass for the Beantown Trolley that stopped all over Boston (good for tired feet).
Things we saw that we really liked were downtown Boston walking some of the Freedom Trail/Faneuil Hall/Quincy Market/USS Constitution at the Charleston Naval Yards/Swan Boats in the Public Garden-Boston Commons/Boston Harbor Cruise/Boston Aquarium. Missed Bunker Hill as it was being restored and was a long uphill walk from the trolley stop in the heat. In the area surrounding Boston we enjoyed Lowell Historical Park and Boott Cotton Mill/American Textile Museum, touring Gloucester, Liberty Ride in Lexington, and Minuteman Historical Park in Concord. The Saugus Iron Works were also interesting. If you like wildlife refuges the Plum Island Wildlife Refuge was very nice and we saw lots of different birds. Newburyport is a very pretty ocean town but it was pouring when we were there so not so scenic. The lobster rolls at Woodmans in Essex were very good. Salem was nothing to write home about. The House of Seven Gables was interesting but I would not go out of your way to see it.
We went the last 2 weeks of August last year. Would recommend spring or fall for the cooler temperatures.
Rob and Kathy