Created during the process of preparing Brazilian cities for the United Nations Conference on Sustainable Development (Rio+20) in May 2012, the Forum of Secretaries of the Environment of Brazilian Capitals (CB27) It brings together the heads of the departments responsible for the environment in the municipalities of the 26 Brazilian state capitals and the government of the Federal District.

Since its founding, CB27 has had institutional and financial support from the Konrad Adenauer Foundation Brazil. In 2017, ICLEI South America, which had been following the Forum's development from the beginning, formalized its partnership with KAS Brazil to contribute to content curation and the institutional strengthening of the group.

The history of CB27's activities, such as strengthening environmental secretariats, exchanging experiences in urban sustainability, and advancing cutting-edge environmental agendas, is compiled in the report "CB27 10 Years – A Decade of Good Environmental Practices and Local Climate Action (2012 – 2022)".