It was incorporated in 1965 by bringing together the Metropolitan Boroughs of Finsbury and Islington.

Clerkenwell in the south of the borough is one of three places (along with Brentford and Westminster) which lay claim to be the County Town of Middlesex. This is due to having the Middlesex Justices of the Peace meet at Clerkenwell Green in the building, which still displays the three seaxes (swords) of the Middlesaxons.