In order to obtain this achievement you will need to sell Undamaged Pelts to all the General Store Merchants. This is quite easy to do, once you unlock New York of course.
There are 9 General Stores Total. 3 to each area. You'll notice a pound symbol on the map if you have discovered it already. Sometimes the game will recognize it without you having to enter, other times I had to walk in the place before it appeared on my map. Look for a building with red trim reading "General Store" and 2 flags hanging from it.
The 3 in the Boston Area are Hancock's Store No. 5, Elizabeth Murray's Fineries, and Child's Still House and Dry Goods. These are spread through each District.
The 3 in the New York Area are Rhinelander's Sugars, De Lancey's Imports & Goods, and Van Brugh's Spices. These are also spread out in all the districts, with one way on the bottom of the East District and the other right on the border of the North and East District.
The 3 in the Frontier Area are The Walking Haberdashery, The Milliner's Wares, and the Murdoch's Barter.
Now with the Frontier being so big and hard to uncover in the map, I will lay out in which part of the Frontier they are located in the hunting section of the map.
The First store is in the Northern Center of Lexington. The Second is Northern West side of Concord. And the third and final store is Mid East side of Monmouth.
(Credit for the video due to TehVGG)
Good luck and happy hunting. If you feel this is inadequate in anyway, please comment before you down vote please.