The stores really were called Penneys (no idiot apostrophe present) until being gradually rebranded in the 70s and 80s.

some examples:

80s: https://commons.wikimedia.org/wiki/File:Downtown_Seattle_Pen...

70s: https://commons.wikimedia.org/wiki/File:FW_Woolworth,_Penney...

60s: https://commons.wikimedia.org/wiki/File:Penneys,_Eastland_Ma...

50s: https://commons.wikimedia.org/wiki/File:StateLibQld_1_46896_...

40s: https://commons.wikimedia.org/wiki/File:Seattle_-_Second_Ave...

Midwesterner here.

My family always used "Penny's" to refer to JC Penny. They also continued to refer to Macy's as Dayton's for years after they had changed their name because the locations were all the same, just the name had changed.

Its funny because I too always felt saying "Penny's" was a regional thing, but more of Midwestern thing.

I'm from northern Ohio (Cleveland area) and it's only reading this thread that I'm learning/realizing that the name "JCPenny" isn't plural or possessive. My family always called it "Penny's" too.

I can understand Penney's or Dayton's since those were people who founded eponymous stores. I suppose we have our answer -- people established a habit of the "S" when that type of naming was so common, and extended it instinctively to all stores even though there was never a Mr. Kmart or a Mr. Circuit City.

Fun tangent: I learned pretty recently that the southern California grocery chain is named after a man with the last name "Ralphs," so it never had an apostrophe and indeed shouldn't have one (in any language).

The Australian English thing to do is to drop the apostrophe, use an optional creative contraction to make the phrase even shorter, and thereby turn the entire thing into a noun :)

I.e. Maccas vs McDonald's

Of course, the official website https://mcdonalds.com.au/about-maccas/maccas-story uses an apostrophe which is now making me have the same reaction as the Germans :( and makes me think it was run through some international filter :p outrageous!

I've also heard people saying "Aldi's" in the US.

Same in Iowa. I grew up talking about going to Penny's (as in JC Penny) or Sernett's or Gibson's (local department stores).