Christopher Ryan had a timely post on Ottawa Start about Connor Court, describing one of the low-rise apartment buildings built in the first half of the 20th Century. As he mentions, O'Connor Street is little more than an onramp to the 417 freeway all the way from the office buildings at the north end through the apartment/commercial district through Centretown.
South of a certain point, O'Connor is mostly mid-rise residential or low-rise commercial, there are a couple of exceptions. I noticed this house for the first time just earlier this month. It's 231 O'Connor, between Cooper and Somerset on the east side:
231 O'Connor is on the 1958 aerials on GeoOttawa, but it isn't on the 1902 (1912 revision) fire insurance maps (unsurprisingly, given the architecture). (Er, on closer look, it appears to also be commercial)
The same day I noticed the house above for the first time, I also took an appreciation for these two houses at numbers 312 and 314, on the west side of O'Connor just north of Frank Street:
The two are clearly twins, although fraternal. They similarly appeared between 1912 and 1958, but even by 1958 they had come into different occupations, the one on the left commercial with a ground floor extended by the time the 1958 maps were taken. But when I checked the fire insurance maps, I discovered something I didn't know: O'Connor Street didn't exist between Lewis and Gladstone in 1912!
There are three other buildings on O'Connor with a house-like appearance but all have commercial uses (except 261 O'Connor at the northeast corner of MacLaren, which is so often obscured by vegetation that I don't have any photos of it!)
Across from the ones above, 311 O'Connor (the side entrance to 328 Waverley) houses a dentist, and the main address has a wedding & event planner, or at least this was the case when I took this photo in 2011. Note: Vrtucar's new head office is in the building just on the other side of the parking lot off screen to the left, and they'll be hosting one of the new RightBike stations this year:
On the next block up, back on the West side of the street, 278 O'Connor contains medical offices, which you wouldn't know without Googling the address, but the giant backlit sign in the yard is a clue:
Jumping up a few blocks, there is a cluster of lowrise buildings at the northeast corner of Lisgar Street, numbers 196, 198, and 200. The middle one, 198, is a four-storey apartment building from 1914 which goes all the way to the back of the lot. Number 200 is connected to 281 Lisgar, which is that one's legal address. Number 196 is the Silver Rose, a florist.
On the fire insurance maps, though, here's where it gets interesting. The 1888 (revised 1901) fire insurance maps show that the previous 198 was identical to the surviving 196, and all three of those buildings were there in 1888. The 'addition' to 200 O'Connor was added sometime between 1888 and 1901. 196 and 200 look to be very well preserved (and 200 actually has the old street name signs attached to its corner)
Neat, eh? So it looks like of all of these house-like buildings, only one, 314 O'Connor Street, is still actively used as residential, plus the elusive 261. Both are rentals. Because who would want to own a house on a traffic sewer?