I am 16 yrs old... have lived in the u.s. since I was 5, but am still a Candian citizen. Do I need a passport to travel from California to the East Coast of the US?

You have dual citizenship? If not, you can apply if one of your parents are Canadian, it would be easier for you.

To answer your question, yes, you need your Canadian passport to travel across the US/

Apply at the Canadian consulate with your birth certificate. You can't do this on line unless you are already have a passport.