Rural and unincorporated areas have strict zoning too. Look at Tuolomne county (https://www.arcgis.com/apps/webappviewer/index.html?id=3e926...) for an example I could easily find a graphic for. The vast majority of privately-held land in the county is zoned RR (brown, 1 unit per 5 acres), AG (1 unit per 18.5 acres), or TPZ (1 unit per 37 acres).