This was the main railroad and telegraph connector between Boston, MA and Portland, ME. As you can see early 4-pin lines are along each side of the tracks. These were outfitted with early threaded insulators and no doubt replaced a threadless route not too long before this picture was taken. By the 1880s or 1890s these telegraph poles were upgraded and 6-pin crossarms installed upon them with CD 145s insulators replacing CD 126s and 127s. See one of my recent accompanying photographs [id=575500614] taken from the same vantage point. By the 1890s AT&T built a long distance lead between the forementioned coastal cities. Sections of it ran along this railroad. Possibly what you see in my 1906 photo (along the left of it) is part of that route.