How do you know that the author is familiar with his setting for last leaf story?

You're asking about O. Henry's short story, "The Last Leaf." It's a great example of how an author's familiarity with their setting can enrich a story. Here are some ways we know O. Henry was familiar with the setting, which is a Greenwich Village apartment building in New York City:

* Detailed Descriptions: O. Henry provides vivid descriptions of the building's exterior and interior. He mentions the "old brick house," the "creaking stairs," the "dingy hall," and the "little ivy vine" that Johnsy watches. These details paint a clear picture of the setting and suggest the author has spent time observing similar places.

* Authentic Atmosphere: He captures the atmosphere of Greenwich Village in the early 1900s, with its bohemian artists, poverty, and the harshness of winter. This sense of realism suggests the author has lived or spent considerable time in the area.

* Local Color: O. Henry uses local slang and colloquialisms, which further indicates his familiarity with the language and culture of Greenwich Village. For example, the characters speak of "Dutch courage" and "the devil."

* Emotional Connection: The story's emotional resonance suggests the author has experienced the anxieties and struggles of living in a crowded city and the impact of poverty and hardship.

While we cannot confirm O. Henry lived in Greenwich Village, the level of detail and authenticity he creates within the story strongly suggest he was very familiar with the setting.