The story
June 22, 1984 - The Aizu line is opened by Japanese National Railways.
November 10, 1986 - Aizu Railway Co., Ltd. is established.
1987:
-Route name, new station name, company badge, etc. are determined.
July 16 - East Japan Railway (JR East) to convert the Aizu line Aizusen opening.
April 27, 1988 - To-no-Hetsuri Station opens.
October 12, 1990 - 15.4 km of the line is electrified, between Aizu-Tajima and Aizu-Kogen Ozeguchi. With this electrification, through services begin with the Tobu Kinugawa Line, Tobu Nikko Line, and the Tobu Isesaki Line.
August 10, 1995 - Minami-Wakamatsu Station opens.
Read the full text
August 7, 1999 - Amaya Station was opened.
July 18, 2001 - Aizu-Sanson-Dojo Station opens.
2002
March 23 - Aizu Mount Express begins operation.
August 29 - Furusato-Koen Station opens.
March 1, 2005 - The express "Minamiaizu" was abolished. Aizu Mount Express starts direct operation to Kinugawa Onsen Station on the Tobu Kinugawa Line.
March 18, 2006 - Aizu Kogen Station was renamed to Aizu Kogen Ozeguchi Station.
2009:
April 18 - A concert is held outside Yunokami-Onsen station
August 23–24 - Rokujizo Station temporarily opens.
August 23, 24, 2010- Ichinoseiroku Jizoson Station was temporarily opened, in the same location as Rokujizo station the previous year. This station would be opened every year until 2014.
2012:
March 17 - Aizu Mount Express begins direct operation to Tobu-Nikko Station.
March 25-The Yume Tour begins operating to Kinugawa-Onsen Station on the Tobu Kinugawa Line.
April 21, 2017 - Tobu's limited express Liberty Aizu starts operations to Aizu-Tajima Station.
From Wikipedia’s article on Aizu Railway, shared under CC BY-SA 4.0.4