California Government Code Section 6700 lists the following days as "holidays in this state":

1. Every Sunday,
2. January 1st,
3. The third Monday in January, known as “Dr. Martin Luther King, Jr. Day,”
4. February 12th, known as “Lincoln Day,”
5. The third Monday in February,
6. March 31st, known as “Cesar Chavez Day,”
7. The last Monday in May,
8. July 4t,
9. The first Monday in September,
10. September 9th, known as “Admission Day,”
11. The fourth Friday in September, known as “Native American Day,”
12. The second Monday in October, known as “Columbus Day.”
13. November 11th, known as “Veterans Day.”
14. December 25th,
15. Good Friday from 12 noon until 3 p.m., and
16. Every day appointed by the President or Governor for a public fast, thanksgiving, or holiday.

Although Columbus Day is on the list of statutory holidays, California executive branch offices will be open today.  Government Code Section 19853 provides that state employees are entitled to the following holidays:

1. January 1,
2. The third Monday in January, 
3. The third Monday in February,
4. March 31,
5. The last Monday in May,
6. July 4,
7. The first Monday in September,
8. November 11,
9. Thanksgiving Day,
10. The day after Thanksgiving,
11. December 25,
12. A personal day chosen by an employee pursuant to Section 19854, and 
13. A very day appointed by the Governor of this state for a public fast, thanksgiving, or holiday

The above list may be subject to conflicting provisions in a memorandum of understanding entered into with recognized state employee organizations.

The California state courts are closed for most business today, however.  Section 135 of the Code of Civil Procedure provides:

"Every full day designated as a holiday by Section 6700 of the Government Code, including that Thursday of November declared by the President to be Thanksgiving Day, is a judicial holiday, except September 9, known as “Admission Day,” the fourth Friday in September, known as “Native American Day,” and any other day appointed by the President, but not by the Governor, for a public fast, thanksgiving, or holiday.  If a judicial holiday falls on a Saturday or a Sunday, the Judicial Council may designate an alternative day for observance of the holiday. Every Saturday and the day after Thanksgiving Day is a judicial holiday.  Officers and employees of the courts shall observe only the judicial holidays established pursuant to this section."