“Don” is an old Spanish honorific for a prominent man, and “Pio” could only refer to Pío de Jesus Pico (1801-1894), the last governor of Mexican-controlled Alta California and the most prominent of early Angelenos. When the town of Girard – today’s Woodland Hills – was laid out in 1923 by real estate developer Victor Girard (1880-1954), its street names were inspired by California’s Spanish/Mexican past: indeed, many called it “the era of the dons”. Don Pio was likely chosen for this street as Pío Pico’s surname was already taken by Pico Boulevard – you can read more about the man there. P.S. Dewey Avenue in Koreatown was known as Don Pio Street for all of one year.