A couple of relevant discussion forums from different boards. One of the posts cites the use of a "hell" from as early as 1956.
http://boards.straightdope.com/sdmb/archive/index.php/t-330838.html
http://boards.straightdope.com/sdmb/archive/index.php/t-345410.html
Also, the following episode titles from TV shows previous to "City" all had the word, the frequency in which it is used in episode titles shows that it wasn't that big a deal:
BOURBON STREET BEAT - "Green Hell" (1960)
THRILLER - "Pigeons From Hell" (1961)
HAVE GUN WILL TRAVEL - "Justice in Hell" (1962)
ROUTE 66 - "Hell is Empty, All the Devils are Here" (1962)
DUPONT SHOW OF THE WEEK - "The Hell Walkers" (1964)
THE FUGITIVE - "Corner of Hell" (1965)
COMBAT - "Hell Machine" (1965)
BOB HOPE PRESENTS THE CHRYSLER THEATER - "When Hell Froze" (1966)
WILD WILD WEST - "Night of the Bars of Hell" (1966)
MISSION IMPOSSIBLE - "Snowball in Hell" (1967)
http://boards.straightdope.com/sdmb/archive/index.php/t-330838.html
http://boards.straightdope.com/sdmb/archive/index.php/t-345410.html
Also, the following episode titles from TV shows previous to "City" all had the word, the frequency in which it is used in episode titles shows that it wasn't that big a deal:
BOURBON STREET BEAT - "Green Hell" (1960)
THRILLER - "Pigeons From Hell" (1961)
HAVE GUN WILL TRAVEL - "Justice in Hell" (1962)
ROUTE 66 - "Hell is Empty, All the Devils are Here" (1962)
DUPONT SHOW OF THE WEEK - "The Hell Walkers" (1964)
THE FUGITIVE - "Corner of Hell" (1965)
COMBAT - "Hell Machine" (1965)
BOB HOPE PRESENTS THE CHRYSLER THEATER - "When Hell Froze" (1966)
WILD WILD WEST - "Night of the Bars of Hell" (1966)
MISSION IMPOSSIBLE - "Snowball in Hell" (1967)