Begin the trip with a stop in Portsmouth, N.H. Maybe a tour of the harbor from Portsmouth.
Across the river is Kittery, Maine. This was already mentioned in an earlier post. The Kittery Trading Post is as good as L.L. Bean but it is better because in the adjoining driveway is Bob's fried seafood. Fried oysters and wild rice. Also other stuff.
Kennebunk has a nice beach but, as I recall, it is not rocky.
Portland. I first visited Portland in the mid '70's. Unfortunately, it is now over-run with Starbucks and other gentrified stuff you find in other cities. BUT, it also has harbor tours and a few places where the locals hang out. Great night life but I am not sure it is a night life for an 18 year old.
As mentioned, take Rt 1 from Portland to points east. Freeport is the home of LL Bean. It is a city with the same mall stores that are probably 5 miles from where you live so don't plan to spend much time there unless your daughter is into mall products.
Moody's Diner is a favorite stop for locals and visitors. On Tuesday, they have Grape Nut pudding.
--- I forgot. Ogonquit, which is between Kittery and Portland. It has the Marginal Way. Marginal Way was a W.P.A. project that established a walking path of about 2 miles along the coast. Every turn of the path offers a different view of the coast. BRING YOUR CAMERA.
Now back to Rt. 1. As mentioned, Acadia National Park in Bar Harbor. If you go there on a clear night, you can see the Milky Way and Andromeda. It is the first location on the east coast of the U.S. to see the morning sun.
Farther east is Eastport. The lighthouse there gets fogged in 180 days per year.
Side Trip..... You may want to skip a day in Maine and if weather prediction is clear, go to Mt. Washington in N.H.
= new reply since forum marked as read