High Quality Content by WIKIPEDIA articles! San Dimas is a city located in the San Gabriel Valley, in Los Angeles County, California. As of the 2010 census, the city had a total population of 33,371. The city historically took its name from San Dismas Canyon in the San Gabriel Mountains above the northern section of present day San Dimas. San Dimas is named in Spanish after Saint Dismas, the repentant and crucified thief