Sebastopol is a city in Sonoma County, California, with a recorded population of 7,521, per the 2020 U.S. Census. Sebastopol was onc…Sebastopol is a city in Sonoma County, California, with a recorded population of 7,521, per the 2020 U.S. Census. Sebastopol was once primarily a plum- and apple-growing region. Wine grapes are the predominant agriculture crop, and nearly all lands once used for orchards are now vineyards. The creation of The Barlow, a $32 million mall on a floodplain in Sebastopol, has converted old agricultural warehouses into a marketplace for dining, tasting rooms, and art, and has made Sebastopol a Wine Country destination.