Does it border one other county? two? three? more? Four Is it the only town that borders this number of counties in CT? Yes. There's a little more to it, but this is close enough.
Marlborough borders four towns, each in a different county.
Marlborough is in Hartford County, and it borders Glastonbury (also Hartford County), Hebron (Tolland County), Colchester (New London County), and East Hampton (Middlesex County).
Nicely done on the quick solve. Now I really need to think of more puzzles.