The Misses Butler

Located on the north-west corner of Powell & Ellis, this one at least has a faint sliver of a story.  Beginning in July of 1921, it was the residence of the great writer of hard boiled detective novels, Dashiell Hammett.  It was the first place he lived in San Francisco.  Presumably it was chosen because he only needed to cross to the south-east corner of the intersection to enter the Flood Building, where he was employed by the Pinkerton Detective Agency.  His novels, written later - especially the Maltese Falcon -  are full of references to locations in the area.

The real mystery here (to me) is -  who were the Misses Butler?  There are numerous references to "the Misses Butler" in society columns of the time, usually in lists of guests at some soiree.  But I can get no farther.