The clam shells road
A clam shells road at Residence Plantation
No rocks of any kind are found naturally within a hundreds miles of Residence Plantation, but sea shells (La Coquille)
were found in abundance in the coastal waters and marshes nearby. Therefore shells were used in construction in place of rocks.
Seashells were normally used in cement by burning shells to create quicklime then mixing it water and either ash, sand, Spanish moss or in this case other clam shells. Historically the Moors brought it to Spain and from there the Spaniards brought the idea to the Americas in the 16 th century which can be seen in Florida as well. Clam shells were used to make it stronger because there are no stones or rocks that are natural to the area.
There is a line of clam shell mounds from east to west in the marshes across Terrebonne Parish (called Indian middens) that were built by native Americans hundreds of years ago before Columbus. Clams were a very important part of the diet of early Native American inhabitants of the Parish and so much clams was consumed that over centuries large islands made of clam shells were common.
Some of the shell islands in the marshes across the Parish were four or five acres in area raising seven feet above the marsh and thirty feet deep, indicating that the native Americans occupied the mounds for centuries to accumulate such a large quantity of shells. Canals were dug through the marsh to mine and transport the clam shells in the area to be used for construction material on roads and wherever rocks would normally be used.
I don't think that people considered the archaeological importance of these mounds, because they were also the burial site of the people and contained many ancient artifacts. A fair number of the mounds are still intact and fortunately now protected and preserved by law.
Oysters grow in abundance in the waters of Terrebonne Parish and are consumed in great quantities by the local people. And clam shells mined at the indian middens oyster shells (La coquille des huidre) were also used for construction.