I recently found pictures of my parents on this corner. Here are my mom and dad.

It's a shame this neighborhood is now long gone. In fact, there is no Union Street in SW DC anymore.

I live in Frederick, Maryland, and have one of these passages connected to my rowhouse. I've been told it is a "horse walk."

These are really common in the UK. Rows of terraced houses (rowhouses) nearly always have a passage to get from the street to the back garden or yard. More expensive houses share the passage just with their immediate next-door neighbour. Cheaper houses often only have one alley per row of houses and then all of the yards have a pathway crossing them to get from one garden to the next (not a lot of privacy if you want to a little bit of sunbathing!) They are called ginnels in the north of England or alleyways in the south. These days people sometimes block them off with a gate and store bikes etc in them. In the north of England there is often a back street as well that runs along the back of the gardens to get from one yard to another. Things in the UK are often smaller than in the US (you should see how titchy our fridges are for example!) so squeezing down a little alleyway really isn't unusual at all!

Fascinating, thanks for the info. You can tell people were skinnier back then.

The small passageway is often called a mouse hole. When the rowhouses take up a long section of the block it was the only way to get from the back yard to the street without walking through the house. In my area (St. Louis) there were often apartments that were entered from the back of the building. On narrow rowhouses the second floor was accessed through an outside rear staircase. The only way to access the rear entrance was through the mouse hole or by walking the length of the block and then all the way back through the alley.