The delicately arched bridge over Calabazas Creek on O'Donnell Lane behind the Post Office was built for horse and buggy around 1900, and is one of the oldest bridges in Sonoma County. Noticeable are yellow bricks from the Chauvet Brickyard. Source: Nearby placard at the Arnold Drive Bridge.

The placard and the official Sonoma County Landmarks page disagree on when the bridge was built, either 1900 or 1920, and how to spell the name of the creek, either Calabezas or Calabazas. Google Maps chooses Calabazas.