People began to open cottage colonies on the Cape in the early thirties, as more visitors began to come to the Cape in their own cars, and as demand grew for inexpensive places to stay.
The Salt Box cottage colony opened on the shore of Bass River, just north of the Bass River Golf Course, in 1938.
Bainbridge Crist, a South Yarmouth historian, wrote about it in The Register in 1978. You can find a copy of his article here: A baroness came, and so did a countess, in the heyday of Yarmouth's Salt Boxes.
The Salt Box development is the set of roads south of the intersection of Oyster Cove Road and Salt Box Road. Source: Google maps.