This same rationale is why the western 1/50 point is between 14th and 15th (no left turn WB Constitution to SB 14th) and US 29 leaves Rhode Island Ave between 7th and 6th (no left turn EB RI to NB 7th).
That resolves a question I came in here to ask.
I had to do a walking clinch of US 50 at the corner of 6th and Pennsylvania, and I would say that if there were US 50 signs eastbound anywhere between the west end of the Mall and I-395, I missed them. (The panel that used to be on NB NW 14th is gone.) Certainly not in the 9th/K/New York area, which is the site of the Apple Store Carnegie Library. I don't recall seeing a US 50 marker at 9th and G (entrance to Gallery Place Metro station).
I do recall seeing an awesome DC-US-1 panel
somewhere, but it was night and I was much more worried/agitated about driving around and around first looking for a nonexistent parking space and then trying to fight my way through traffic to Union Station.
Edited by Markkos1992 to fix quote.