I live in Maryland and telecommuted to California. Do I need to pay California income tax?

No, you pay taxes in the state where you physically perform your work. The only reason you would file a California tax return is if CA taxes were withheld.

Slightly more accurate: You file taxes from the state which is your tax home. For example, I live in CA, but travel for business often. I do NOT file taxes from all the states I may visit for business nor any other countries. CA gets it all.