By far the fastest way to get this is to hang out in the main part of Boston city. In the city alone, there are right around 75 locations. After doing some side quests and misc objectives, I had roughly around 60 locations. I ran around the city for about half an hour, and skyrocketed up to 100, and found some pretty neat locations along the way!!
http://fallout4map.de/w/index.html#3/-66.48/-78.84I am putting this here as a reference. It's a neat interactive map that Reddit has offered up, and it shows the locations of all key collectibles in the game. What I would suggest is going for the bobbleheads, magazines, giant creatures etc etc, and then heading into the inner city to mop up the rest of your locations. It really isn't much of a grind, and can actually just be gotten over time if you finish the game. If you really want to grind it, though, this is a good way to go.