Europeans settled this area in the late 17th century and quickly began to establish large plantations along the Ashley River, whose rich land was the source of wealth. Several of these compounds have been preserved, and it's hard to understand life in this area without visiting them. The three major ones are all fairly close together on Ashley River Road (State Road 61), about 40 minutes northwest of central Charleston: Drayton Hall, Magnolia Place, and Middleton Place. If you purchase the Heritage Passport, it includes admission to Drayton Hall and the gardens at Middleton (normally $25 each or so).
It's well worth the drive out here. You may wish to avoid heavy traffic times (you're cutting through the edge of the Charleston urban area), but exploring these buildings and the grounds is both aesthetically and historically pleasing.
You reach Drayton Hall first: built in 1736, it remained in the family for 200 years before being turned over to the National Trust for Historic Preservation. During those years, very little was done to update it, change it, or even paint it, so it remains an amazing example of what these buildings actually looked like in their day. The Georgian architecture is wonderful, and the site along the Ashley is pleasant, with lots of aquatic life at the river's edge. Admission to Drayton Hall includes a guided tour, which added immensely to our visit. The docents appear to be all volunteers, but ours was extremely knowledgeable and (usually) pleasantly opinionated.
This area was hit hard by Hurricane Hugo in 1988, and there's an interesting photo album of how that affected Charleston and this site in particular. The century-old trees, whose crowns met over the Ashley River Road, giving it a cathedral-like feel, were largely wiped out by the winds. You can sense that absence as you make your away along the river to Middleton Place.
The large attraction here is the gardens, an intricate and careful 18th-century design. Fountains, sculptured ponds, carefully laid out viewpoints--it's a smaller colonial version of Versailles. There's also a "living history" area where all the work that slaves and servants did to make these places run is demonstrated: weaving, candlemaking, blacksmithing, cooking, etc. The house is not included on your Heritage Passport ticket but can be toured for an additional charge (we passed--there was plenty else to do here).
We spent a very pleasant afternoon at these two places and came away understanding life in this time and location a lot better.