In 2000 when we moved to Camden, the locals referred to it as 'Radio Free Camden', the cellular signal was so spotty. We use Verizon now and it improves all the time.For sure. I used to have a dedicated cell booster antenna on my radar pole in order to get reception. I also remember having to drive to the top of Cadillac mountain to get reliable service to call my girlfriend at the time, that would have been in 2000. Today it’s a different world, although I agree with Accnick that two carriers is the way to go for more or less full coverage along the coast from Boothbay to Bar Harbor. Verizon is great in most of Penobscot bay. Further east ATT works better. There are definitely anchorages that I go to sometimes because they are both secluded and beautiful, but I can also watch a movie on Netflix if I want to.
Good info in these answers. I didn't know some were carrying two providers for better coverage.