Thanks to the NY Times I learned of Here is Where whose mission is

to find and spotlight little known and unmarked historic sites throughout the United States.

I really love this story from the article:

The Marriott Wardman Park Hotel in Washington, Mr. Carroll's hometown, has agreed to install a marker that commemorates a moment on Nov. 27, 1925, when the poet Vachel Lindsay was timidly approached at dinner by a busboy who placed three poems he had written next to Lindsay’s plate. Lindsay was so impressed that he shared them with his audience at a poetry reading that night, prompting journalists to report on the "busboy poet." His name was Langston Hughes.