The “Black Gate” was added to Newcastle Castle between 1247 and 1250, forming an additional barbican in front of the earlier north gate of the castle. It consisted of two towers with a passage running between them. On either side of the passage was a vaulted guardroom. There was a drawbridge at the front (facing west) and another at the rear. There was also a portcullis which could be raised and lowered to seal the entrance passage.
The original building would probably have had a flat roof, but in 1618 James I leased the gatehouse to a courtier, Alexander Stephenson. Stephenson substantially altered the gatehouse, rebuilding the upper floors. Stephenson then let the Black Gate out to various tenants, one of whom was a merchant, named Patrick Black. It was he who gave his name to the Black Gate.
Eventually houses were built along both sides of the passageway, and one part of the building became a public house. By the early part of the nineteenth century, the Black Gate had become a slum tenement, housing up to sixty people.
Blackgate was leased to the Society of Antiquaries of Newcastle upon Tyne in the 1880s, which extensively restored it between 1883 and 1885. It was the Society that added the top floor and pitched roof. The Society has held regular meetings there ever since. The drawbridges to the front and rear have been replaced by wooden footbridges.