1966	August	Oono Development founded Representative Director Teruo Ōno Construction business (Civil Engineering Works)
1973	November	Reorganized as Oono Development Inc. Representative Director Teruo Ōno Capital stock JPY 5,000,000
1975	March	Construction business permit granted (by Ehime prefectural governor)
1980	February	Company name changed to Oono Associates Inc.
	May	Industrial waste treatment permit granted
1982	November	Regular landfill treatment site opened
1984	November	Capital stock increased to JPY 20,000,000
1985	February	Controlled landfill disposal site opened
1986	February	General waste treatment permit granted
1988	April	Waste incineration facility no. 1 installed
1989	November	Waste incineration facility no. 2 installed
1992	February	Capital stock increased to JPY 70,000,000
1993	July	Specially controlled industrial waste treatment business permit granted
1996	June	Waste incineration facilities no. 3 and 4 installed
2002	May	Advanced leachate treatment facility completed
2007	June	Regular landfill disposal site expanded
	August	Controlled landfill disposal site expanded
2009	October	Institute of Environmental Science and Technology (Oono Labo) established
2011	April	Tōon Treatment Facility’s name changed to “Frep Tōon” Combined treatment facility (with 2 rotary kilns) constructed and starts operation
	July	Contaminated soil treatment permit granted (first permit in the prefecture)
2012	May	Opened Tokyo Branch Office
2013	March	Large heavy machine SK2200D delivered and starts operation
	April	Large heavy machine SK3500D delivered and starts operation
2014	February	Authorization for low-concentration PCB waste detoxification Minister of the Environment’s authorization no. Heisei26-3 (2014-3)
	December	Authorization for low-concentration PCB waste detoxification Minister of the Environment’s authorization no. Heisei26-9 (2014-9)
2015	July	Opened Osaka Branch Office
2016	July	Large 800-ton LTM1800NX crane delivered and starts operation
	August	Change of representative director Representative Director Teruo Ōno appointed Chair of the Board of Directors Director Tsuyoshi Ōno appointed Representative Director
2018	March	Authorization for low-concentration PCB waste detoxification Minister of the Environment’s authorization no. Heisei30-9 (2018-9)
	May	Contaminated soil treatment permit granted(RK144)
2019	July	Opened Fukuoka Sales Office
	September	Opened Strider Courses in Mattera Forest(Social contribution activities)
	October	Controlled landfill disposal site expanded
2020	April	Lithium-ion battery detoxification and recycling business starts
	September	Opened Kyushu Branch Office
	November	Opened Chita Office
2022	April	Teruo Ōno appointed Representative Director