Petaluma's first library was an Odd Fellows Library that was established in 1858 and opened to the public within a decade. By 1878, its ownership was transferred to the City of Petaluma as part of the Rogers Free Library Act and the Library with the original collection of books established by the Odd Fellows Library Association was relocated to the upper floor of the old City Hall.

In 1906, the new Petaluma Library opened at Fourth and B Streets. This Library was one of the 2,509 library buildings constructed with the aid of Carnegie funds. The Carnegie Library was designed by local architect Brainerd Jones and built from locally quarried stone. The building features the largest freestanding leaded glass dome in Northern California. With few changes through the decades, the building served as a Carnegie Free Library until 1976. In 1988, it was listed on the National Register of Historic Places. It is now the Petaluma Museum, a historical museum with research library.

By the late 1950’s, increased usage and limited space demonstrated the need for a larger facility with space to provide modern library services. Studies indicated that alternate solutions, such as enlarging the old building or opening a small east-side branch, would not be feasible. In three elections, bond proposals for a new Library failed to get the needed two-thirds vote.

In 1973, as population and demand grew, the need for a new facility increased and a plan for a more centrally located building was developed. With the commitment by the City Council and the County Board of Supervisors to allocate Federal Revenue Sharing Funds to cover one-half the cost, a bond issue for the balance was approved in a special election in 1974.

 The new Library, located at the corner of E. Washington Street and Fairgrounds Drive opened in 1976. The Petaluma Regional Library has an area of over 25,000 square feet and features an interior of exposed heavy timber trusses and natural wood finished walls. The Library is constructed with brick-veneered walls and a copper roof. Several improvements have been made in recent years, including expansion of the Forum Room, creation of a bookstore that is operated by the Friends of the Petaluma Library, and upgrades to the adult restrooms.