In Chapter XVI, when Mary goes to the theater, there is talk of all the rich families living in England at the time. Mr. Flower talks about the mayor and mayorness of Northborough and how, "They're as rich-well, as rich as Americans". Northborough is a village in Cmabridgeshire in the East of England. It is an extremely small town. Ironically there is also a Northborough, Massachussets that is home to many wealthy families which could also be the place that Mr. Flower's is alluding too instead of Northborough, England. 

Sources:  “Northborough, Cambridgeshire.” Wikipedia, Wikimedia Foundation, 20 Apr. 2020, en.wikipedia.org/wiki/Northborough,_Cambridgeshire.