I'm going to start a new series on the blog about small streets that people may not be familiar with in the neighborhood, which I'm calling Forgotten Streets. The first episode is on Pine Street.
The street is very short, about 1/4 of a regular-sized block, and basically exists as a way to turn left from 16th Street onto Park Road, which hits it at an odd angle. There's a turn lane from 16th that turns into Pine. The only building on it is the Shrine of the Sacred Heart church, a Catholic church, which is why there's an honorary "Sacred Heart Way" sign under the Pine Street sign.
Not sure why it exists, really, as it's at an odd angle that doesn't match any other streets. Here's the current map on Google, and you can see it on this old map from rockcreek's Flickr as well.