Pyle decided to continue teaching at his home base in the Wilmington Delaware - Brandywine Pennsylvania area -- but instructing only those who he considered had great professional potential. The result was something now referred to as the Brandywine School of illustration.
The most lengthy biography I could find on the Internet regarding Arthurs was in this PDF file. Below is an extraction of that part of the document.
Although Arthurs illustrated a great deal of popular literature, his real specialty was illustrating historical texts. His pictures were as historically accurate as he could make them. He did several murals of historical subjects for the State House in Dover, Delaware, and for the Minnesota State capitol building and produced a long series of historical paintings for DuPont Company calendars and the DuPont Magazine. Many of these were published in book form in the American Historical Scene in 1935. The historical illustrations occupied most of Arthurs' attention after 1920, but he also painted landscapes, not only of local scenes but also in Florida, the Western states, and Europe.
Source: Elzea, Rowland and Elizabeth H. Hawkes, eds. A Small School of Art: The Students of Howard Pyle. Wilmington: Delaware Art Museum, 1980."
Examples of Arthurs' work are presented below. I find his painting style a bit too heavy for my taste, but it was mainstream -- especially in the period 1900-1920.
Modred was a traitor to King Arthur.
Two illustrations from an article Arthurs wrote for the November 1908 issue of Scribner's Magazine.
Civil War Scene.
Benjamin Franklin in Philadelphia.
A somewhat sloppy work. I don't know if this was simply a sketch or if it was published. The warships are not convincingly portrayed -- too sketchy and the perspective seems off.
A Great War vintage illustration supporting the war effort, though I don't know where it was published. Arthurs seems to have used artistic license here because submarines were usually destroyed using depth charges. Unless they were caught on the surface, as shown here. But about the only way a German submarine could be caught on the surface by a warship this closely would be if it had been damaged by a depth charge and had to surface. Fortunately for Arthurs, most viewers were probably ignorant of anti-submarine warfare, so such details didn't really matter.
Probably from around 1926. The reproduction was intended to be two-color, a common magazine practice in those days.