When Charles and Albert return to the restaurant/hotel after dinner at Laura's, the windows of the restaurant say "Nellie's" even though the name of the restaurant was changed to "Caroline's" long ago and said "Caroline's" earlier when they first arrived on the stage.
An old clip was used of the diner at night showing the name Nellie's on the windows when several seasons ago it was changed to Caroline's.
Burr Oak, Iowa was the "city" in this episode. The real Burr Oak is a small, unincorporated community.
Morphine usually has to be injected, so it's unclear what effect drinking has. In powder form it's usually called heroin.
The real Charles Ingalls moved the family to Burr Oak Iowa for one year, 1876-1877, well before Laura was married in 1885. The true location of their move after that time was DeSmet South Dakota territory.
Charles claims he can't leave the city because of his wife's job and his kids' schooling. But that's exactly what he did leaving Walnut Grove, on top of abandoning his sawmill, his farm, his freight company, his best friend and his only living grandchild. Bad premise.
Laura would not have had her father and brother stay in the hotel since she and Almanzo added a room onto their house last season.