Not having a map that would show the limits of St.Antoine Ward in 1891, it is difficult to confirm that St. Alexandre St. was part of it. St. Alexandre goes from South to North. On my current map, civic numbers would start around 900 and go to about 1400. There might have been a different numbering system in those days. Nowadays, it is less than half a mile long. St.Antoine St. did not use to go that far in the East bond area; it has replaced Craig St. in the Eastern part of the city. The West/East point is St.Lawrence St.
St.Antoine Ward would probably have included the area south of Dorchester Blvd (now REné-Levesques Blvd) and the area West of Bleury St.
A book has been written about the Golden Square Mile in Montréal. I believe that this is the Title as well. The southern border was St.Catherine St. and the Northern one probably Pine Ave. It included the area where McGill College is now located.But that would be north of the St.Antoine's ward. The latter being a blue collar living area, The GSM was habitated by the upper or upper middle class people.