2000: Latvia, Legal Recognition of Latvian Sign Language
"Latvian Sign Language (Latvian: latviešu zīmju valoda) is a sign language commonly used by deaf people in Latvia. Linguists use LSL as an acronym for Latvian Sign Language.
The Official Language Law of 9 December 1999, which came into force on 1 September 2000, gave Latvian Sign Language a legal status in Section 3.3, which stipulates: 'The State shall ensure the development and use of the Latvian sign language for communication with people with impaired hearing."
Source: https://en.wikipedia.org/wiki/Latvian_Sign_Language