Comic Legend: There is no explanation for the S that Jughead wears on his shirt.
As far as the comics themselves go, that is accurate.
[A]stute reader John Morgan ‘Bat’ Neal...linked to an old article from Entertainment Weekly from the early 1990s when Archie Comics was celebrating their 50th anniversary, and it quoted Bob Montana’s widow, Peg Bertholet, on the topic of Jughead’s S.
Bertholet proclaimed that the S was based on a hill in the area where Montana grew up (Haverhill, Massachusetts) called Squirrel Hill.
Well, there is, in fact, a Squirrel Hill nearby Haverhill, and it is well established that Bob Montana based a great deal of the original Archie characters on the residents of Haverhill, MA (if you did not know that, well, now you do – Haverhill, specifically Haverhill High during the years Montana attended it, was the inspiration for Riverdale and most of the various characters, like Mr. Weatherbee and Pop Tate).
Now to find this inspirational point next time we find ourselves in front of a map.