California taxes capital gains at its ordinary income tax rates, not its sales tax rate. A capital gain from the sale of property located in California is taxable by California, as well as by your state of residence (your state of residence can tax ALL your income, regardless of its source.)
https://www.ftb.ca.gov/file/personal/income-types/capital-gains-and-losses.html
You must file a non-resident California tax return in addition to your home state Oregon return. You'll be able to claim a credit on your CA return for the taxes paid to OR on the capital gain, so you won't be double-taxed.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
