Detail of map courtesy of Rob Pitingolo.
Take a look at Rob’s full map here and compare it to Georgetown’s. Georgetown appears to have fewer alleys than the rest of central DC. It’s interesting to speculate why that is. Presumably during the formation of the village’s grid, Georgetown was as dependent (if not more) on horses and stables as the rest of the historic city was. It’s odd that many large blocks don’t have any alleys at all (of course, larger homes had carriage passageways from the front to the back to allow a horse to be housed in the back without an alley).
One explanation could be that the alleys once existed, but now they don’t. One example of this is Dent Place in the West Village. Many homes on that street have unusually long backyards because in the 1980s, the city allowed the residents to close the alley and claim the land for their own.
Just eyeballing it, it also seems that the West Village has more alleyways than the East. This is consistent with GM’s observations. Many of the alleyways in the West Village are large and are lined with garages. Most (but not all) of the East Village alleyways have a parking pad at most. GM’s not sure why it turned out that way.