JNR

To celebrate its 50th post, Jeremy Rosenberg has handed over the reins of his "Laws That Shape L.A." column. The focus of this week's guest feature: the special overlays and site-specific designations that cover 60 percent of the city's geography.

During the 1920s, the federal government passed a pair of laws that continue to this day to be hugely consequential to the modern practices of city planning and zoning. The two laws also planted the seeds of the planning profession.