Allies Day, May 1917 by Frederick Childe Hassam is one of the most celebrated pieces from his "Flag Series," portraying the patriotic fervor of New York City during World War I. The painting captures Fifth Avenue in a moment of exuberance and solidarity as it is adorned with the flags of the Allied nations, including the United States, France, and the United Kingdom, fluttering in the breeze. The composition presents a vibrant cityscape alive with motion and color. The broad avenue is lined with stately buildings, their facades serving as a backdrop to the kaleidoscope of flags.