Answer: 2151 Sacramento Street

The street of course shares its name with the capital of California. You will reach an area across from which you can see an area full of dog-walkers and sunbathers, which is Lafayette Park. From there, the speaker (Sherlock Holmes) began looking for evidence that Sir Arthur Conan Doyle (Holmes' "creator"), occupied a home in that area, based on the plaque at this address.

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