where in the world?

I bet I won't get everything.

Melrose MA
Somerville MA
Boston MA
Arenal, Costa Rica
Domenical, Costa Rica
Paterson NJ
New York City NY
Plymouth Meeting PA
Madison WI
Dennisport MA
Burlington MA
Oakland CA
Portland OR
Chestertown NY
Lenox MA
Enfield CT
Belfast Ireland
Christiana DE

I have omitted airplane flights, even overnight ones.

I really feel certain I'm missing something. Possibly Arlington VA though I can't place when that was, and it's possible I'm thinking of 2011. I'll update later if I figure it out.

[Edited to add Plymouth Meeting PA and NYC]