Hawaiʻi Sign Language (HSL; Hawaiian: Hoailona ʻŌlelo o Hawaiʻi), also known as Hoailona ʻŌlelo and Old Hawaiʻi Sign Language, is an indigenous sign language native to Hawaiʻi. Historical records document its presence on the islands as early as the 1820s, but HSL was not formally recognized by linguists until 2013. Although previously believed to be related to American Sign Language (ASL), the two languages are unrelated. In 2013, HSL was used by around 40 people, mostly over 80 years-old. An HSL-ASL creole, Creole Hawaiʻi Sign Language (CHSL), is used by approximately 40 individuals in the generations between those who signed HSL exclusively and those who sign ASL exclusively. Since the 1940s, ASL has almost fully replaced the use of HSL on the islands of Hawaiʻi and CHSL is likely to also be lost in the next 50 years. HSL is considered critically endangered. History HSL is not itself a pidgin, but alternate names for the language are documented as Hawaiʻi Pidgin Sign Language or Pidgin Sign Language. This is due to an inaccurate historical association with the spoken language Hawaiʻi Pidgin. Linguists who have begun to document the language and community members prefer the name Hawaiʻi Sign Language, and that is the name used for it in ISO 639-3 as of 2014. Village sign use, by both d/Deaf and hearing, is attested from 1820. There is the possibility of influence from immigrant sign later that century, though HSL has little in common today with ASL or other signed and spoken languages it has come in contact with. The establishment of a school for the deaf in 1914 strengthened the use of sign, primarily HSL, among the students. A Chinese-Hawaiian Deaf man named Edwin Inn taught HSL to other d/Deaf adults and also stood as president of a Deaf club. However, the introduction of ASL in 1941 in place of purely oral instruction resulted in a shift from HSL. Recognition HSL was recognized by linguists on March 1, 2013, by a research group from the University of Hawaiʻi at Mānoa. The research team found a letter from Reverend Hiram Bingham to Reverend Thomas H. Gallaudet from Feb. 23, 1821. The letter described several instances of deaf Kānaka Maoli communicating to Bingham in their own sign language. The initial research team interviewed 19 Deaf people and two children of Deaf parents on four islands. Eighty percent of HSL vocabulary is different from