Prior to June 1998, California's trial courts consisted of Superior and Municipal courts, each with its own jurisdiction and with its number of judges fixed by the Legislature; prior to 1951, the Petaluma Justice Court was one of twelve such inferior courts in the County. The Justice Court (also known as the Petaluma Justice's Court; more formally designated as the State of California's Justice Court for Petaluma), had jurisdiction over the City of Petaluma and surrounding area of southern Sonoma County, California.

The Petaluma court, like other justice courts, was an inferior local tribunal for the adjudication of minor causes and the preservation of the peace. By the Act of March 16, 1850, which divided up the state into judicial districts, "the term of office of a justice of the peace was fixed at one year. Two justices were allowed to each township, also two constables, the officers who serve the processes of the court. The jurisdiction of a justice extended to the limits of the township for which he was elected. He had cognizance of actions on contract, for damages, and to recover specific property, when the amount or value did not exceed $200. In 1851, his powers were considerably increased. He had jurisdiction of actions to recover money, for damages to personal property, for fines, penalties and forfeitures, actions on bonds, enforcement of lien on personal property, actions to recover personal property and judgment by confession, where the amount in all these cases did not exceed $8,500, and on a bond taken by him if the amount did exceed that sum, cases of forcible entry and detainer, and the trial of the right of mining claims. The criminal jurisdiction embraced vagrancy, disorder, petty larceny, assault and battery, breaches of the peace, and all misdemeanors punishable by a fine of not more than $500 and not more than one year's imprisonment. In 1863, forcible entry and detainer cases were transferred to the county court, and the civil jurisdiction was reduced to amounts not exceeding $300. In 1870, the jurisdiction of cases of misdemeanor was extended to fines of $1,000 and imprisonment for one year: but in 1874 it was reduced to fines of $500 and six months' imprisonment. In 1863, the term of office of justices and constables was increased to two years. The new constitution preserved the justice courts as before." (source: Wells, Harry Laurenz, 1854-1940. History of Butte County. San Francisco : H. L. Wells, 1882.)

The Petaluma Justice Court was reorganized in 1952 as part of the State of California's inferior court reorganization program authorized by the voters as California Proposition 3 in 1950, which combined the offices of the township justices of the peace and city police court judges; the Petaluma Justice Court and other, local municipal courts were combined as the Petaluma Judicial District Court or more formally, the State of California's Municipal Court for the Petaluma Judicial District) on Jan. 1, 1952.

A number of other reorganizations and consolidations of the County's District Courts took place over the next four decades until the District Courts and other inferior courts were absorbed into the Superior Court following another voter-authorized reorganization in 1998, California Proposition 220.