I know what the code says but I have never really been sure what it means. I have never been around an ungrounded building. I think it was the GI bill housing requirements or something but every house I saw in the DC area used <small EGC> grounded Romex, even before they had 3 prong receptacles (post war). Houses older than that were wired in BX. I have never seen K&T either.
The old buildings I saw as Fla state inspector were wired in pipe or some kind of armored cable. I thought I might see some K&T at the 1926 Ringling mansion in Sarasota but it was EMT or rigid everywhere. No galvanizing though, all black painted. There was some "new" work in BX/AC but nothing NM. All of the renovations used EMT or MC.
