Penngrove , California 94951, USA is a small, unincorporated community in Sonoma County , between Petaluma and Cotati at the intersection of Old Redwood Highway and Petaluma Hill Road, nestled in the foothills of Sonoma Mountain . Located in the remnants of a historic grove called Penn's Grove, it was previously a north bay freight rail station on the Northwestern Pacific Railroad as well as a center for egg and chicken farming, much like its close neighbor Petaluma . Every year Penngrove celebrates the 4th of July with a parade organized by the Rancho-Adobe Fireman's Station located at the corner of Main Street and Old Redwood Highway.