@back2work Thank you for this helpful information.

Which way is up?

The view is of the side of the wall and the ceiling.

That's a gas pipe? There could have been a small wall heater in there. The patched hole in the ceiling was a flue. Looks like dirt.

Thank you @seabornman!

I am not quite sure if it’s a gas pipe. I looked up the name on the front and still could not tell it’s purpose. Such an odd placement in a closet.

I learned something new! Never heard of a flue; just googled it. Thank you.

The black stuff looks like soot to me; agree w/ Seabornman that some kind of fossil fuel appliance was in there at some time in the past.

Is the pipe galvanized? The cap appears to be. I wouldn't expect to see galvanized gas pipe. Nor would I expect a space heater in a closet, though it might have been a furnace. Any suggestion that ductwork might have once been there? It could also have been a gas water heater - any plumbing nearby?

Another clue is that part of the wall hasn't been painted as recently as the rest, as if it had been behind something immovable.

@DavidR yes, I do believe it is galvanized but there is no plumbing really close by to that side of the house (that I can tell). There is a bathroom in the hallway (middle) on the second floor. This bedroom is in the back of the house on the second floor.

Built in 1919. No suggestion that ductwork was there at all. The house hasn't had much work (except the kitchen (17 years ago) and hardwood floors (approx 50+ years ago).

I'm having the most difficult time attaining the original plans for the home. In Chicago, anything prior to 1950 takes a lot of research to find that information.

This is the general layout of the home. Living Room is front of the house. There are radiators within each room. There is also a chimney in the living room. Thank you all!

Wait, how many capped pipes are in this closet? I'm a little slow (guess I need another caffeine hit), and I just noticed that the pipe in the third photo isn't the same one that I see in the first two photos.

Can you stand back farther and snap some more photos, for a larger overall perspective?

I love a good house mystery. :)

@DavidR There are 2, one at the top and the one about 5ft below the first one.

Any clues in the attic above? Say, a patch in the attic floor, or can you see the ceiling patch from up there?

I'm guessing from the size and floor plan that this house was probably built by a fairly well off original owner.

Here's a crazy thought. Maybe at one time there was a face sink in this bedroom, to the right of the closet. That wasn't at all uncommon, though I'd more expect it in what was probably the master bedroom (front of the house).

Let's say that the sink was initially supplied only with cold water. (Stay with me here, I'm speculating.) The owners wanted more comfort first thing in the morning, so they installed a small water heater in the corner of the closet next to the sink. The cold water from the sink plumbing went in the bottom of the water heater, and the hot water was drawn off the top. That would explain the two pipe stubs, and the height difference.

But you have only 2 pipes, so how was it fueled? The absence of a gas stub, and the fairly large amount of soot around the area, might suggest that it was oil fired. The closet doesn't seem very roomy, so they might have fed the oil to it from a small kerosene bottle nearby.

Maybe it was a water heater like this.

Check the floor in the closet for clues, too. (water damage, patches, etc.) Possibly there was a water heater in the old kitchen downstairs and the flue was routed through the floor & closet on the second floor & then through the ceiling attic & roof. Soot could have accumulated in the closet due to a leaking flue connection?

That theory doesn't explain the water pipes--one could have supplied the up stairs bathroom but the other? Dunno. It's early & I have had 3 sips of coffee so I'm still in dunderhead mode.

Our old house had a small sink in what would have been the maids room that we had removed during a remodel. I’m also guessing just soot and dirt from many years gone by.

Thank you all for so much insight! I really appreciate it. Here are a couple more angles.

What's the diameter of the pipe? I don't guess you'd want to unscrew one of those (slowly) and see what comes out? You'd have to be prepared with pipe dope or Teflon tape if they're active. Inquiring minds want to know.

@Seabornman HAHA! Oh noooo, I will have to ask my plumber to do that when he comes in a couple of weeks.

I would go to the basement to look for more puzzle pieces. Like for evidence of an old coal fired boiler and patches where the flue might have exited thru the basement ceiling.

Thanks for the extra pictures. After looking at your last photo, I'm even more certain that something formerly in that corner was difficult or impossible to paint behind, but not quite right up against the wall. I don't think it was just a flue pipe.

Was this the original location of an expansion tank for hot water heat? I have a house from that era with an expansion tank in an upstairs closet and the dimensions look similar. The new expansion tank is only a few feet from the new boiler so the change was probably part of the boiler change.

I like Lyndee Lee's idea better than my own.