Gregory House occupies apartment 221B in House M.D.
The address is a clear reference to 221B Baker Street, the fictional London home of Sherlock Holmes. House is deliberately modeled partly on Holmes, so the apartment number reinforces the connection between detective work and medical diagnosis. House solves illnesses by examining clues and eliminating explanations, much as Holmes solves crimes.
The address also helps characterize House’s private life. His apartment is a recurring setting where colleagues and friends see a less formal side of him, although it remains a place associated with solitude, music, games, and unconventional behavior. The show uses the space as an extension of House’s independence.
The number is easy to misremember as 221A or as a different address from another television adaptation of Holmes. In House M.D., the important reference is specifically 221B. The apartment is in Princeton, New Jersey, not Baker Street in London; the location is a tribute rather than a literal continuation of Holmes’s setting.