Re:Route 9 in Maine
I'm going to assume you mean Route 9 (the Air Line) from Bangor to Calais and then cross over to New Brunswick... slim pickins', I'm sorry to say. My best advice is to grab a bite in Bangor or wait until you hit Canada. Dysart's is pretty good, just off the highway technically in Hampden, but close to Bangor. There used to be a good restaurant in Calais called the Chandler House, but it is gone now. St Stephen NB has a little seasonal fish and chip place on the river that is good. Try the lobster roll! St Andrews is a little tourist town with several restaurants and a fine old hotel, the Algonquin.
St John has some good pubs, especially in the area of the Public Market, which is worth a visit.
I'm sorry I can't help more- my info is a few years old now. FYI in Canada and the eastern US, Irving gas stations are known for their clean restrooms and some have pretty decent diners attached. We ate at several throughout the Maritimes.