Near the end of its first session in 1850 the California legislature passed an act composed of forty-nine sections entitled "An Act to provide for the appointment and prescribe the duties of Guardians." This act directed judges, before appointing a person as a guardian of a minor, or insane or incompetent person, to require such persons to give a bond with sufficient sureties to the minor or insane or incompetent person. Every bond given by a guardian was to be filed and preserved in the office of the Clerk of the Probate Court. In 1861, the guardianship act of 1850 was amended. When the laws of California were codified in 1872 those concerning bonds of guardians and the recording thereof were included in the Code of Civil Procedure in sections 1754, 1756, and 1765 and remained in effect at least through 1905. Bonds today are still required of guardians in California. This publication comprises two parts. The first part is an all-name index containing over 4,000 entries of every bond principal, bond surety, and ward named in each Sonoma County bond of guardian listed in the second part. The second part is a tabulation of the 1,700 Sonoma County bonds of guardians dated 1852 through 1907 (original, recorded, or both) housed in the Sonoma County Archives. The information given for each of the bonds of guardians includes: the probate case number, the name of the bond principal, the names of the bond sureties, the name of the person or entity to which the bond principal and sureties are bound, the type of probate case (minor, incompetent, or insane person), the amount of the bond, the date of the bond, and the book and page(s) on which the bond is recorded.