Like many surrounding neighborhoods, the growth of Los Angeles-proper and the expansion of corresponding freeways resulted in a transition to working-class housing and industrial developments throughout the 20th century.
Over half of the population of Diamond Bar was identified as being of Asian descent, per the most recently available census data. Those of Latine descent account for another 1/5th of residents.
Each of these demographics has played a vital and vibrant role in much of local culture and business up to the present day.