The Petaluma Historic Commercial District is comprised of 174 acres containing 63 buildings and one object of historic significance.

The Petaluma Historic Commercial District represents the development of commerce in the city from the mid-nineteenth century to the end of the Second World War. It also provides a diverse and well designed collection of commercial buildings, the architectural importance of which is unmatched in Sonoma County. Although the district has changed its appearance somewhat since 1945, it retains a high degree of architectural integrity and maintains its associations to the historic period.

Commercial activity in the downtown area began even before the founding of the town in 1852. In the half-century before that, the area passed from the control of the Petaluma Indians to that of the Sonoma Mission. It then became the subject of conflicting land grants. After the start of the Gold Rush, a few white settlers trickled in, drawn by the access that the Petaluma River provided to markets in San Francisco. By the end of 1851 the number of new inhabitants grew large enough to warrant laying out the town. A plat was drawn up in 1852, and residents began erecting woodframe buildings, both residential and commercial. By the end of the year the town had three hotels, several stores and a number of warehouses. Petaluma and its commercial district grew rapidly in the 1850s.

Petaluma and its commercial district grew rapidly in the 1850s. The town became the main shipping point for the surrounding agricultural region, which specialized in grains and dairy products. San Francisco, reached by steamship in five hours, provided a ready market for all that the area produced. Petaluma's port became one of the busiest in the state. The local population grew to about 1,500 by the end of the decade. Stores began to specialize; a bank, a newspaper office, and several fraternal halls appeared. Some new buildings were of stone or brick construction and gave the district a more substantial and permanent appearance. The town, which had grown to be the largest in Sonoma county, incorporated in 1858.

Excerpted from the NRHP nomination.