Cazadero was the Northern end of the Northwestern Pacific Railroad's narrow guage line in Sonoma County. Cazadero is the largest area of the SMRR layout, reaching from Duncan's Mills to the end of the NWP line at Cazadero.

The Sonoma Mountian Railroad layout models the following areas after the Northwestern Pacific would leave Duncan's Mill.

Area 1: Leaving Duncan's Mills, entering the Austin Creek watershed.