In preparing for these lectures, I scoured the Washington newspapers and documented their extensive reportage of this event.
The blog Imp of the Diverse has several posts on coverage of Esperanto in the press in its early years. The latest post, posted today, is . . .
1910: Zamenhof to Arrive in Washington
Here we find a bit of background, a newspaper photo (reproduced here), and some snippets from the press and from Zamenhof's correspondence in anticipation of the 1910 Universal Congress.