When I saw Myko Clelland's tweet this morning, my reaction was "Wow! Just, wow!"
It appears on page 343 of Willard Cope Brinton's book, Graphic Methods for Presenting Facts (McGraw-Hill, 1914).
Myko included a brief description in his tweet, but let me elaborate by quoting from pp.342-343 of Brinton's book, and you'll see why I liked the photo so much:
"Educational material shown in parades gives an effective way for reaching vast numbers of people. Fig. 238 illustrates some of the floats used in presenting statistical information in the municipal parade by the employees of the City of New York, May 17, 1913. The progress made in recent years by practically every city department was shown by comparative models, charts, or large printed statements which could be read with ease fro either side of the street. Even though the day of the parade was rainy, great crowds lined the sidewalks. There can be no doubt that many of the thousands who saw the parade came away with the feeling that much is being accomplished to improve the conditions of municipal management. A great amount of work was necessary to prepare the exhibits, but the results gave great reward."
Don't you just love it? A gigantic mobile poster session!