The Los Angeles County Regional Planning Commission (Commission) (defendant) granted to the Topanga Canyon Investment Company a zoning variance to establish a mobile-home park on 28 acres of land in Topanga Canyon. The ordinance governing zoning variances stated that a variance should be granted only when, due to special circumstances applicable to the property, a strict application of the zoning ordinance deprived that property of privileges enjoyed by other properties with identical zoning in the vicinity. The data in the Commission’s report, which the Commission relied upon to grant the variance, stated that the proposed mobile-home park would leave 30 percent of the acreage in its natural state, would help to satisfy the demand for affordable housing, and would be on hilly and steep land. The report did not, however, include facts about the surrounding properties. The Topanga Association for a Scenic Community (Association) (plaintiff) opposed the variance. After the variance was granted, the Association appealed to the county board of supervisors, which denied the appeal. The Association sought administrative mandamus in the superior court and the court of appeal, but was again denied. The Supreme Court of California reviewed the denial of mandamus.