Don't know that this helps with the archaeological record (I'm a
historian/architectural historian), but swept yards are, in the South
anyway, associated with African-American sites--slave as well as free, well
into the twentieth century and probably even current.  Also found in mill
villages, and with tenant houses and the like, often swept into patterns,
sometimes quite intricate--swirls and such.
 
URS Greiner has just finished a phase I archaeological survey on Sandy
Island in Georgetown Co., SC.  Sandy Island is located between the PeeDee
and Waccamaw Rivers across the Waccamaw from Brookgreen Gardens and north.
It was just about the northernmost point of tidal rice culture and though
it is a freshwater island (geographically very rare in SC and surrounds),
it is associated with the state's sea island Gullah culture.  Only a
handful of whites have ever lived on the island.
 
We know we have six discrete plantations in existence by the early
nineteenth century.  Although Georgetown's records were destroyed during
the Late Unpleasantness (in Chesterfield where they had been sent for
safekeeping)  a very nice collection of plats survives showing detailed
plantation complexes with slave settlements, rice barns, landings,
overseers' houses, miscellaneous buildings, a threshing mill, stables, main
houses, and ditched, diked, and trunked rice fields.
 
Mainland plantations on both rivers included rice fields, high ground,
uncleared swamp, and timbered land on the island.  The island continues to
be the location of an African-American community, Mountrena (spelling
varies) populated largely by descendants of the slaves.  It was founded in
the 1880s by Phillip Washington, a former slave driver on one of the
plantations, who purchased Mont Arena Plantation at the south end of the
island.
 
The island still has no bridge or ferry, potential development was averted
and SCDOT now owns the majority of the island which will be protected, used
as a wetlands mitigation area and possibly for off-site mitigation for
archaeology.  As the island is so isolated and the high ground is useless
for farming, it has remained virtually pristine.  It was used for timbering
and as a hunting preserve for much of the late nineteenth and twentieth
centuries.  The children on Sandy Island go to school on the mainland via
SC's only schoolboat.
 
We would expect swept yards--
 
Sandy Island is a unique and amazing place--if this rather rambling account
has piqued interest, contact Wayne Roberts at the South Carolina Department
of Transportation, Columbia for additional information.
 
Suzanne
 
 
Suzanne S. Pickens
URS Greiner
Florence, NJ
The opinions expressed are those of the author.