The American Sign Language, since its invention, has found widespread use within the deaf community as well as with researchers and linguists. For quite a long time, though, language researchers and linguists did not consider ASL sign language as an actual language with a proper linguistic structure and phonemic characteristics. Then, in 1960, Dr. William Stokoe, an American linguist and teacher of English at Gallaudet College, created Stokoe Notation and proved that ASL sign language does indeed have the linguistic features to make it as much a proper language as oral languages.
The curious part was that Dr. Stokoe, before he joined the hearing-impaired school Gallaudet in 1955, knew practically nothing about sign language or Deaf culture. His language theory was based on his observations of the way his students signed at each other, and, when put forward, it was met with skepticism initially from both the deaf community and the linguists. It was only after he invented the Stokoe notation that they came around to agree with his view that a language didn't have to be verbal to be a language. Having sign language acknowledged as an actual language was a momentous step for the deaf community. It strengthened the feeling that Deaf cultural identity didn't have to be dictated by and didn't have to depend on limits set by spoken languages.
Stokoe Notation was the first phonemic script in the history of American Sign Language. Dr. Stokoe detailed it in his 1960 book Sign Language Structure and later, in 1964, published A Dictionary of American Sign Language on Linguistic Principles. He devised fifty-five symbols and showed that each sign operated on the parameters of location, movement, and hand shape.
These original fifty-five symbols were later found to be insufficient to meet all sign language requirements, and subsequent researchers have modified and added to these symbols to suit particular needs. With all this adding and modifying, we now have many different systems of Stokoe Notation rather than one standard system.