In 1939, well, almost. Dorothy Ella Inghram earned her elementary teaching credential in 1939 after student teaching at an East Highlands (near San Bernardino) school. In 1941 she accepted the position that made her the first Negro teacher in the county.
To learn more, see: https://www.sbvcfoundation.org/sbvc-alumni/hall-of-fame/Dorothy_Ella_Inghram .
She was born in San Bernardino and was educated at San Bernardino Valley College and University of Redlands. Hers was not an easy journey as she described in this article published in 1979:
Circa 1941 image from http://www.sbcity.org/about/history/pioneer_women/as_seen_from_within.asp .
The term Negro is used here as it was the accepted description in 1939 even though at present it is out of favor. To learn more about it, see: http://www.aaregistry.org/historic_events/view/negro-word-history .