The borough was formed from seven civil parishes and extra-parochial places: Furnival's Inn (part), Gray's Inn, Liberty of Saffron Hill, Lincoln's Inn, St Andrew Holborn Above the Bars with St George the Martyr, St Giles in the Fields and St George Bloomsbury and Staple Inn.
Previous to the borough's formation it had been administered by two separate local bodies: Holborn District Board of Works and St Giles District Board of Works.