I think it is determined by where the glaciers melted and receded to the north, resulting in the difference between the North Shore beaches and the South Shore beaches of Long Island, Cape Cod, Nantucket and Martha's Vineyard. The North Shore beaches are rocky from the remaining glacial debris, while the South Shore's are crisp, clear, outwash sand.
Links:
Maidstone
Jones Beach Pitch and Putt
Garden City
Sankaty Head
Nantucket GC
Maybe Links:
Shinnecock
Timber Point
National
Edgartown GC
Hyannisport
Not links:
Newport
Friars Head
Fishers Island
Misquamicut
It is determined by where the glaciers ended:
Long Island, as part of the Outer Lands region, is formed largely of two spines of glacial moraine, with a large, sandy outwash plain beyond. These moraines consist of gravel and loose rock left behind during the two most recent pulses of Wisconsin glaciation some 21,000 years ago (19,000 BC). The northern moraine, which directly abuts the North Shore of Long Island at points, is known as the Harbor Hill moraine. The more southerly moraine, known as the Ronkonkoma moraine, forms the "backbone" of Long Island; it runs primarily through the very center of Long Island, roughly coinciding with the length of the Long Island Expressway.
The land to the south of this moraine to the South Shore is the outwash plain of the last glacier. Known as the Hempstead Plains, this land contained one of the few natural prairies to exist east of the Appalachian Mountains.