I grew up in Concord/Walnut Creek in the 60s. When I visited the area last year I did not recognise it!
I live in Concord and Monument Street is called little Mexico. I won't even stop at a store around there because the street and parking lots are filled with guys loitering.
Also, the police were stopped from stopping anyone in that neighborhood for expired tags because they were accused of racism.
Walnut Creek = VERY expensive real estate.