The inside joke for DC-ers, natch, is that there is no J Street — which is also why Jeremy Ben-Ami adopted the name for his lobby.
(I’ve heard two stories about why: One is that in the early 19th century, the printed I and J looked overly similar. Another is that Pierre Charles L’Enfant, the capital’s designer, despised John Jay, the first chief justice of the Supreme Court. Here’s Snopes debunking the latter theory.)
Thanks to Jason Epstein for the snap.