The county was named after the cities of Åbo (Turku) and Björneborg (Pori). Åbo was not only the provincial capital but centre of government for all of Finland while it was a part of the Kingdom of Sweden. It also included the Åland Islands.
By the Treaty of Fredrikshamn in 1809 Sweden ceded all its territories in Finland, east of the Torne River , to Russia. The county was succeded by the Governorate of Åbo-Björneborg in the Grand Duchy of Finland as part of the Russian Empire.