I made a bit of a road-trip on Labor Day, and noticed this place between Camden and Hartsville. Beaver Dam Trading Post sat just up the hill from an old mill pond. While the mill was never in operation (that I can recall) while I was growing up, it sat there idle for years and years as the pond water rushed over the spillway. In general my parents didn't want us going near it for fear that something would collapse, but I recall getting up to the windows at least once, and seeing all the works and millstone still inside the place. Of course, despite driving past the mill at least a dozen times every year, and despite fancying myself as a shutterbug with my 35mm constantly at the ready on these family trips, I never thought to take a single picture of it until after it was gone.
Also at the side of the lake by the mill was an unlabelled upside-down "L" shaped pipe which was the outlet for an artesian well. This flowed 24/7/365, and we would always make our parents stop there so we could drink from this marvel. Once our dog got into the spirit as well, and jumped out the car window to join us at the pipe, managing to break her leg.
The small spurt of development that brought the Trading Post seemed to have put paid to the old mill and well. This is complete speculation but I suspect that people locating around the lake were distrustful of the old spillway, and that increased septic usage made a potable well somewhat iffy. At any rate, the mill went first, and the well a few years later.
After the route from I-20 through Bishopville to Hartsville developed, we travelled this stretch of road much less often, and in my case usually at night. To me it seemed that Beaver Dam Trading Post was doing neither better nor worse than you would expect for a convienience store in what was still a pretty sparse and rural area. It wasn't packed, but there were always a few cars there. This Administrative Court decision shows that they were apparently owned by a former Lee County Magistrate and got a permit to sell beer & wine to go in 1999. This set of game-day driving directions shows that they were closed by 2009. Judging from the growth of the tree around the gas island, I would say maybe 2007 or 2008, but given that the interior is still intact, probably not much earlier than that.
UPDATE 21 Sep 2010: I should probably note that although most google searches list this spot as "Hartsville", it is actually well outside the town limits and is much closer to the unincorporated little community of Kellytown.