A few years ago we excavated a hand-dug well near Charleston, SC which dated
to the immediate post-Civil War period.  The soils were coastal sands and
clays with a fairly high water table.  Like the other well described in this
thread, ours had evidence of a pit excavation in the upper levels (top 60
cm) but then was clearly excavated from the interior below that level.  It
was lined with unmortared bricks with the headers forming the ring.  A
square base of 1-inch thick boards underlay the last course of bricks at a
depth of approximately 4 m below present ground surface.  These boards
rested on gumbo clay.  Water levels in this well fluctuated widely depending
on the time of year.  When we first located it in early spring, it was
filled to the top;  when we excavated in mid-summer the water level was 2 m
below present ground surface.  Given the proximity of the well to a tidal
river (less than 100 m), I wouldn't bet on the quality of the water, but it
was the only thing available other than groundwater seepage in low areas.
Similar wells were identified at other sites within this project, so the
construction method appears to be typical for this area, dating back to 18th
c. sites.

                Lucy Wayne