My son is crazy about trolleys, so when we go to New England next summer, we need to visit one, but I don't want to see more than one.

Which is the best?

Kennebunkport, Maine
WIndsor Locks, CT
New Haven, CT

Kennebunkport! Right outside a nice town, and the museum itself covers a very big area. Admission includes rides on the working trolleys (usually 2 or 3 in rotation ) on a fairly long track --about a mile. There's a big "barn' with other trolley's that you can climb on/in. If you're there over 4th of July weekend, they have some kind of festival .
The other 2, in my opinion, are just not as nice (and the locations--ouside of Hartford and New haven CT (actually East Haven, i think) are not as scenic

ttt

I haven't been to the CT ones, but the one in Kennebunkport is a lot of fun. We took a trolley ride and then spent some time climbing around on a lot of others. I believe there's a roundhouse there too (can't remember if it worked). Have fun!

We ended up going to the one in Kennebunkport. It was very nice with two different trolleys working that day. The track goes about 1 mile out and back. There are loads of other trolleys in the sheds to look at. THere is also a workshop where they are actively restoring the trolleys.