As 1960s sprawl filled Brandywine Hundred, some architects called for a new kind of community, a mixed-density development that would combine single-family homes with less expensive town houses and apartments and leave open space. New Castle County zoning did not allow this approach, so Valley Run Building Corporation and its Philadelphia planners spent three years convincing the government to give them large-scale variances. Weatherboarded apartments form long units that undulate with the topography.