The majority of the 1890 census was destroyed in a fire and only fragments exist, none of them covering Brooklyn. Thus, ancestry.com has put together an "1890 Census Substitute," part of which consists of the 1888-1890 Brooklyn City Directory. So, since I'm going back in time (at least when I don't get caught up in death certificates and early censuses), and I've already brought the Mulcahys back to 1905, and looked for them in 1900, we're looking for 1890. When I went to find and post the City Directory links I'd found for Matthew Madigan and Michael Mulcahy, though, I discovered that ancestry.com has recently added to the U.S. City Directory records that they have published! They now cover 1879-1900. So, I'm going to be looking to see who else and what else I can find.
This, just off of a quick initial search, is Mathew Madigan, truckman, living at 85 Luquer St. As you can see from the image, there's really no other information included. We can hopefully use this to do things like figure out where the Toners lived in 1880, so we can find their census listing, figure out when the Mulcahys moved into 85 Luqueer St and when Matthew Madigan moved out (which would possibly be when he died), possibly even figure out when Michael Mulcahy immigrated, if he suddenly shows up in the city at some point.
Isn't this exciting?