Poster for, or maybe recalling, Wake Up American Patriot's Day in New York City.
A lot of cities and towns across the nation were having patriotic rallies in April 1917. New York had one that occurred on April 19th, the anniversary of the Battle of Lexington and Concord in 1775. April 19 is celebrated as Lexington Day in some locations on the East Coast, or at least it was so celebrated.
The woman dressed as Paul Revere is likely Jean Earl Moehle who portrayed Revere in the event. In some accounts she's cited as being an actress, but in others a suffragette. Whether or not she ever worked as an actress I don't know, but she was definitely a suffragette and therefore I think the citations to her being an actress are in error.
Moehle got a fair amount of camera time due to the event, although she'd been in the public eye before, including appearing with Inez Milholland Boissevain at an event in which she worked on a Maxwell car in 1914. She wasn't the only feature of the event, of course.
Other riders at the Wake Up America Day event in New York.
Moehle, it might be noted, was working in France for the YMCA at some point during World War One and continued employment with the YMCA at least as late as 1920.
A feature of the event was the participation of various ethnic societies, which turned out to show their loyalty to the United States.