The two cities made the top 15 list of cities that added the most residents over a period of a year that ended in July.
The information comes from a new Census Bureau report.
According to their data, LA added more than 18,000 people, while Irvine added a bit over 11,000 new residents thanks to a homebuilding surge.
The number one spot on the list went to San Antonio, Texas -- which is up more than 24,000 residents.