Check the Secretary of State website, this will provide information on the company and the agent for process. You can order copies of the Articles of Incorporation from the agency as well.
The Secretary of State only maintains information regarding officers, directors, and agents for service of process for corporations, and managers, chief executive officers and agents for service of process for LLCs. The identity of the owners is not public and is not registered with a public entity.
I have attached a link to the Business Entity Records Order Form which will enable you to order all publicly available information on a corporation or LLC but you will not be provided with actual ownership information.
IMPORTANT NOTE: This response was prepared by Adina T. Stern, A Professional Law Corporation for informational purposes only and is not intended as legal advice. The information available in this answer is not intended to create, and receipt of it does not constitute, an attorney-client relationship. The information on legal issues available here is not a substitute for legal advice from an attorney who is familiar with all of the facts surrounding your particular situation who is licensed in the appropriate jurisdiction. This answer does not create an attorney-client relationship.
As was noted above, information about actual owners is not in the public record. However, if it is a small LLC or corporation, you might be able to figure it out. They may name themselves as an incorporator or as the resident agent. It may require being a bit of a gumshoe. Good luck.
LEGAL DISCLAIMER: Please note that this comment does not constitute legal advice nor has an attorney-client relationship been created.The law may vary depending on the state in which you reside or the jurisdiction where the activity took place. This comment is intended only to give some direction in which to seek further guidance.
If the company filed a Form D "Notice of Exempt Offering of Securities" with the SEC when issuing securities you MIGHT find some information on owners in the SEC's online database at sec.edgar.gov. You will not find information on owners on the California Secretary of State's website.