NAIP 2016 aerial imagery county mosaics (3-band RGB – also known as “CCMs”) for California are also available from the USDA Geospatial Data Gateway:

https://gdg.sc.egov.usda.gov/

Basic instructions to download county mosaics from Gateway:

Click on Get Data green button
Select State for order:  California
Select County(ies) of interest
Scroll down to the Ortho NAIP category and select “2016 National Ag. Imagery Program Mosaic”…