This screenshot is from the opening of the Dragnet episode
Narcotics that first aired January 30 1969. Who knows how much earlier the footage was shot but there sure wasn't much of "The Hill" left at that time.
While on the subject, it has been discussed here that the series
Perry Mason had a habit of using the same actors in different roles but
Dragnet was essentially a repertory company when it came to bit parts.
This gentleman, Howard Culver...
and this lady, Virginia Gregg
each appeared in thirteen episodes, never playing the same character twice. There were only 98 episodes of the 1967 - 1970 color Dragnets produced so that's a pretty impressive average. Is the series still great? Of course it is!