Named in 1925 for Mabel Gladys O’Sullivan (1894-1988), then-stenographer for City Terrace developer Walter H. Leimert. O’Sullivan was the fifth of eight kids born into a Danville, IL coal mining family. By 1920, she was plying the steno trade at an Illinois railroad office; by 1924, she was living in Los Angeles and working for Leimert. Her boss clearly thought highly of her, as he promoted her to assistant secretary – a high-level position, not the same thing as an administrative assistant – at his various enterprises by 1928. It’s not clear what happened next, but O’Sullivan apparently lived in San Bernardino County from 1933 until 1939, then returned to L.A. to work as a steno at Wright Aero Ltd., an aircraft company. She was listed as a director of Signal Petroleum in 1950. Not much else is known about her, except that she never married or had kids.