cotton was cultivated in both the old world and the new world.

and in both 'worlds', there were some wonderful hybids. Sea island cotton is grown (primarily) on the sea islands along the atlantic coast--these extend from Georga/N Florida area right on up to Long Island.. (and to geologically, really, right up to cape cod, which is now a peninsula, but was once a barriar island.) -most of the barriar island spend time connecting to the main land, and then, being washed away again in winter storms, some, like coney island, and rockaway island, (in NYC) have become permentently connected to the main land.

sea island cotton is very similar to eygptian cotton.. a very smooth, very long fiber, and very strong fiber cotton, that can be spun very fine, so you can get thread counts of over 300 threads per square inch(only silk has finer fibers/threads)

sea island, is both a variety, (a specific type of cotton --sea island variety) and cotton grown on one of the several sea island (off the coast of NC) that are the original home to the variety.

unfortunately, the term sea island is used rather loosely and not all cotton labeled sea island cotton is really grown there.. and some cotton grown on the island is not the long staple length variety. (a more pressing concerns, is these islands, like hilton head, are being 'developed' as resorts communities, and many of the old farms are being put out of business.)