The view today looking south on Elm Street in Hillsdale, with the Disney Channel and Discover Channel high-rises across the Ventura freeway from the Warner Ranch. The pool is across the street from the  Wilson home, but was not used in any episodes.  Beyond the pool and the trees is Tommy's house and beyond that the Hollywood Hills (which doubled as Walton's Mountain in that series). (Warner Bros photo)

Where is Hillsdale?

               The Mitchell’s and the Wilson's, Dennis’ best friend Tommy Anderson, plus the residents of the Elkins' house (not always occupied by Lucy Elkins) along with Miss Esther Cathcart, and Margaret Wade (not sure where her house was), all lived in Hillsdale.... along with Otis Quigley the grocery owner and Lawrence Finch who owned the drug store. Would that be in California, Michigan, or Wyoming, or New York, or Hillsdale, New Jersey?  

              Hillsdale may be in California: in "Mr. Wilson's Paradise", Henry says the Island of Happiness, in Mexico, is only "2 hours away by jet". Also, the signs in grocer Quigley's market do say "California", along with the fruit they are advertising (See" Dennis' Penny Collection", Season 2). But just as Georgia peaches sell out of state, so does California fruit. Henry said in "Out of Retirement" that George helped him shovel snow....which would eliminate the warmer  states for sure.  Also, in "The Haunted House" the ghost, played by Harold Gould,  says he has to catch the 1222 train to Florida, so maybe Hillsdale is in the Midwest or South.

and this:

DtM as much as told us it was in California throughout the entire series without ever actually coming out and saying so.

* In a first-season episode, Mr. Wilson mentions how Mr. Pomeroy has come to visit from the state capital that is over 500 miles away. That in itself narrows it down to California, Texas and Alaska, and the setting definitely is not either of the latter two.
In this same episode, the script goes to lengths to not pin down the location. It's stated multiple times that the Canadian Crested Warbler has never been seen "in this state," and how many people do you know that use that exact phrase multiple times to describe where they are or live?
* In the final season, we're told it's only a couple-hour drive to San Diego for that two-part episode involving the San Diego Zoo.
* Also in the final season, and coincidentally in a separate two-episode story arc, we know Washington D.C. is a lengthy flight. Definitely longer than the three hours or whatever that's stated, but still lengthy. -- from Sitcoms Online Forums

             One Internet posting credited "TV Guide's 50th" program that said the fictional town of Hillsdale was in California.    We may never know what the writers had in mind when they chose Hillsdale, but one thing is for sure: it appeared to be a fine place to live and raise a family. –  Dennis!  website Editor

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