He would feature cityscape views such as this many times across his career, but normally without flags decorating such a large part of the scene. He then focused on them several times over a period of just a few years and this body of work became one of the most important contributions that he made. In this particular composition we find allies' flags together in a show of strength and friendship. The French, UK and US flags appear in varying sizes, leading from the foreground all the way through, further back along the right hand side. There are also some smaller flags on the opposing side of the road, though most of the buildings on that side are visible. We can appreciate the beautiful architecture found in this street, with detail suggesting at rather than delivered precisely, just as was the way with the Impressionists. The blurred detail helps to give an impression of movement, which was entirely suitable for cityscape works such as this.
Besides the detail on either side of the road, there is also a good number of people wandering through the street itself. They are small by comparison and this helps to deliver perspective to the piece. We understand that the artist is working from high above for this painting, looking down on the vehicles and pedestrians below. In the far distance there seems to be an opening, and a widening of the street, allowing greater sunlight to come in. Perhaps it is there that we meet a square of some sort, or alternatively the architecture may simply be a little lower at that point of the street. Whilst these are gloriously patriotic in tone, much of the content here would have been inspired by Hassam's knowledge of French art, with Monet and Pissarro having already completed fairly similar types of paintings in the earlier era of French Impressionism.
Allies Day, May 1917 is around a metre in height, just over when including the dimensions of the frame which holds it currently. The setting is believed to have been Fifth Avenue, a famous street which the artist covered several times over a period of just a few years. The flag paintings by Hassam were actually unveiled just after the end of the war, meaning that whilst the content covered the American entry into the war, the paintings would actually be seen first when celebrations had already begun. Today, this timing would not be known by many. Hassam's own artistic approach was a perfect balance between American and French influences, and so to see the stars and stripes alongside the tri-colour here seems entirely appropriate, particularly considering how this style of composition had already been carried out successfully a number of times by the likes of Monet and Pissarro.