The County of London was a county of England from 1889 to 1965, corresponding to the area known today as Inner London. It was created as part of the general introduction of elected county government in England, by way of the Local Government Act 1888. The Act created an administrative County of London, which included within its territory the City of London. However, the City of London and the County of London formed separate counties for "non-administrative" purposes. The local authority for the county was the London County Council (LCC), which initially performed only a limited range of functions, but gained further powers during its 76-year existence. The LCC provided very few services within the City of London, where the ancient Corporation monopolised local governance, as it still does. In 1900 the lower-tier civil parishes and district boards were replaced with 28 new metropolitan boroughs. The territory of the county was in 1961. During its existence there was a long-term decline in population as more residents moved into the outer suburbs; there were periodic reviews of the local government structures in the greater London area and several failed attempts to expand the boundaries of the county. In 1965, the London Government Act 1963 replaced the county with the much larger Greater London administrative area.
See wiki.familysearch.org under "London" and also under "Middlesex" for key information about Greater London's jurisdictions and records, plus links to indexes, reference aids and Family History Library holdings.
Crime, poverty and social policy, London Lives 1690-1800 is fully searchable with 240,000 manuscripts from eight archives and fifteen datasets, giving access to 3.35 million names. This site is FREE to use.
The proceedings of the Old Bailey, London's central criminal court, 1674-1913. A fully searchable edition of the largest body of texts detailing the lives of non-elite people ever published, containing 197,745 criminal trials held at London's central criminal court. This site is FREE to use.