I am planning to apply for UCLA, UC Berkeley, UPENN, UC Irvine, UC Riverside, UC Davis, UC San Diego, SJSU, and Sonoma State. Do any of these colleges require me to write a supplemental essay(s)?
Not sure what you mean by supplemental but, there’s no essay on the CSU application (SDSU and Sonoma) but, UCs require a ‘personal statement’ The prompts are the same for all UC campuses ( they actually share the same application). Read about it here.
http://admission.universityofcalifornia.edu/how-to-apply/personal-statement/
I don’t know about the UPENN ap.
2 essays for all the UC’s. I think a why my major for SJSU, don’t know about Sonoma.
UPenn has a “Why Penn (based on what school you’re going to whether it’s SEAS or Wharton)” and more essays if you’re applying to a dual degree program.