High Quality Content by WIKIPEDIA articles! North Tustin is a census-designated place and unincorporated community in Orange County, California. The population was 24,917 at the 2010 census, up from 24,044 at the 2000 census. It is Orange County`s largest Census Designated place. It is not located in the city limits of Tustin, using Santa Ana as its proper mailing addresses according to the USPS, and a 92705 ZIP Code. The name was changed from Tustin Foothills in 2005.