Been doing more research and finding more things than I found two years ago when I first started searching.
From two years ago, I found that in 2000 Scotch Plains used chickens to see if the West Nile Virus was in the area. That was basically all I found that connected Scotch Plains and chickens at the time, though now I think I have an idea where they kept the chickens in 2000.
What's new that I've found: Mention of Scotch Plains in this book published in the early 20s called American Poultry Advocate Vol XXX No 1. Was also mentioned in The Poultry Item which was published in like 1911. And in several other poultry books around that time.
In 2013, a man from Scotch Plains was helping a town change its ordinances on chickens.
Also found this on ClerkBase under Scotch Plains: "Domestic animal" shall mean any cat, dog, or livestock other than poultry. And then goes on to talk about dogs and cats, and something under 'Moneys to the Treasurer of the Township' that mentions 'for payment of damage to or losses of poultry and domestic animals, except for dogs and cats.'
So it seems like my town had some well known chicken breeders at the start of the 1900s, poultry are not considered domestic animals, and it sounds like maybe poultry is allowed. There is nothing that says outright that chickens (poultry) aren't allowed and if they are allowed how many one can have for their size of land. Looks like I may have to finally call someone or go to the municipal building. Not looking forward to that.