By 1910, Philip Little had been identified as an artist who was "fully open to American national influences." "I am distinctly American in my ideas as regards the future of art," he wrote, "which I believe should break away from the trammels of the European schools..." Unlike many of his American contemporaries, Little never studied in Europe, and while he did visit England, he did not make the grand tour of the Continent that was almost mandatory for a young artist during the last quarter of the nineteenth century. Nevertheless, he was not disinterested in modern art and was said to be a great admirer of Monet, whose style supposedly influenced his own.

Due to his father's successful business ventures in Lawrence, Massachusetts, Little could devote his time to the pursuit of art without financial worries. He studied graphic design at the Massachusetts Institute of Technology in Cambridge in 1875 and 1876, worked for the Forbes Lithograph Company in Boston from 1877 to 1880, and then studied drawing at the school of the Museum of Fine Arts in that city in 1881 and 1882. Four years later he moved to Salem, Massachusetts, where he shared a studio with Frank Benson, whom he had met at the Museum of Fine Arts school. Little lived in Salem for the rest of his life, spending many summers on MacMahan Island in Maine. He was involved in local civic, political, and military affairs in Salem and earned the rank of major as a member of the Massachusetts National Guard (1887-1901). Also active in the art world, Little was a founding member of the Guild of Boston Artists and served as the curator of fine arts at the Essex Institute in Essex, Massachusetts, for some years. His early design training was useful during World War I, when he was hired by the United States government to design camouflage patterns for ships.

During his early years, Little concentrated on lithography and etching, and he was undoubtedly influenced by Benson to pursue them further. He did not paint seriously until about 1903. That year he made a trip to Jamaica, during which he kept a detailed sketchbook with notations about weather conditions, temperature, and the like. He said later that, under the spell of the Caribbean climate, he "seemed to awaken from a sort of sleep and began to see sunshine, as well as nature, in silhouette." Within a decade Little was being loosely aligned with the American Impressionists with whom he shared an interest in light, atmosphere, and seasonal changes. "Rain, snow, sunlight and shadow, all are interpreted by him with an equally thorough understanding," wrote one critic in 1913, who went on to state that Little's paintings were the "embodiment of spontaneity, vibration and strength." Another writer cautiously called Little's works "impressiomistic to an extent" but noted that his palette was often more tonal than high keyed.

Little's exhibition record confirms that he was most active as a painter from 1903 until around 1930, and especially during the 1910s. In 1907, the Rowlands Galleries in Boston sponsored his first solo exhibition, which was followed in 1910 by an important show of forty-five works that traveled to the City Art Museum in St. Louis and to the Cincinnati Art Museum. St. Lous was the site of another one-artist show in 1913, and the Colorado Springs Art Society and the Portland (Maine) Society of Art held exhibitions of his work in 1913 and 1914, respectively. Goodspeed's Book Shop in Boston hosted a display of his drawings, lithographs, and etchings in 1919 and sponsored several presentations of his graphic art during the 1920s. Little first exhibited at the Pennsylvania Academy of the Fine Arts in 1889, but his works appeared there more frequentlybetween 1908 and 1930. He submitted paintings to the annuals of the National Academy of Design from 1911 to 1922. During the 1920s, the Guild of Boston Artists held several exhibitions of his paintings, etchings, and watercolors to local critical acclaim.

An overwhelming majority of Little's exhibited paintings, if not all of them, were landscapes or marines. Many of the titles identity the scenes as being in Maine or Massachusetts, with a few set in Washington, D.C., or in Minnesota. During his lifetime, the artist was recognized not only for his paintings of Salem and its environs but also for his love of the sea and sailing vessels, although he did paint the occasional figural work. One of these, The Connoisseur of 1913, features a woman seated lone in an interior contemplating a Japanese vase. It is highly reminiscent of paintings with similar themes by Boston artists Joseph DeCamp and William Paxton.

September Moon: The Weirs by Moonlight was included in Little's first solo exhibition at the Rowlands Galleries in 1907 and in the annual exhibition of the Pennsylvania Academy of the Fine Arts the following year. It is characteristic of Little's landscapes in subject matter and technique. The setting is probably the Massachusetts coast near Salem, or perhaps it is in Maine or in the vicinity of MacMahan Island. Three boats are anchored for the night near a collection of weirs, that is, closely placed stakes that are driven into the mud of a shallow tidewater flat in order to catch fish. The unseen moon illuminates the water, partially dissolving boats and weirs alike in a shimmering light. The white light and blue water, laid on the canvas with a freedom of handling and a thickness typical of many of Little's paintings, contrasts with the darker tones of the shoreline that surrounds the scene. Around 1919, Little treated the theme of weirs again in an etching entitled The Weirs. A painting with the same title, which may have been related to the etching, was shown at the Portland Society of Art in 1914. The relationship of either of these works to September Moon: The Weirs by Moonlight is not known.