For a nice non-highway route from Concord, consider Rt 28 thru Wolfeboro to Ossipee, then Rt 16 north to Rt 25 east to Wesrbrook Maine. Then Rt 295 to Brunswick and Rt 1 takes you right up to Ellsworth.
An alternative route with just a little highway time is Rt 4/202 east to Northwood, then Rt 4 thru Rochester and Sanford, catching Rt 111 in Alfred to Biddeford. Then 95N to 295 to Brunswick and pick up Rt1.
I've done both routes towing trailers and the latter towing a 26' sailboat. I think the best part of the trip to BH is Rt 1 beginning Freeport.
I used to make the annual MDI trek, wish I was doing it right now! Have fun up there!
