221B Baker Street
Most stories and adaptations
221B Baker Street is the London home of Sherlock Holmes in the canon stories and in most adaptations. The owner and landlady of the house is Mrs Hudson.
221B Baker Street first appeared in A Study in Scarlet when Holmes and Watson rented it from the landlady, Mrs Hudson.
Watson moved away after his marriage to Mary Morstan following the events of The Sign of the Four . Watson had said that the monthly rent Holmes pays was almost equal to the full value of the house. 221B Baker Street was created by Sir Arthur Conan Doyle. being an entirely fictional address at that time. In the United Kingdom. postal addresses with a number followed by a letter may indicate a separate address within a larger, often residential building. Baker Street in Holmes’ time was a high-class residential district, and Holmes’ apartment was probably part of a Georgian terrace.
Sir Arthur Conan Doyle’s Intentions 
When the Sherlock Holmes stories were first published, street numbers in Baker Street only went up to 100, which was presumably why Sir Arthur Conan Doyle chose a higher street number for the location of his hero, to prevent any person’s actual residence from being affected by the stories’ popularity.
The section north of Marylebone Road near Regent’s Park – now including 221 Baker Street – was known in Conan Doyle’s lifetime as Upper Baker Street. In his first manuscript, Conan Doyle put Holmes house in «Upper Baker Street,» indicating that if he had a house in mind, it would have been there. However, a British crime novelist named Nigel Morland claimed that, late in Conan Doyle’s life, he identified the intersection of Baker Street and George Street, about 500 metres south of Marylebone Road, as the location of 221B.