Dearth began his artistic training with the Connecticut portraitist Horace Johnson. He went to Paris in 1883 and worked in the ateliers of Antoine Herbert and Aimé Morot. By 1887 Dearth had opened a studio in New York. Throughout his career he wintered in New York but spent most of his time in France at his home at Montreuil-sur-Mer in Pas-de-Calais, Normandy.
Dearth was first represented in an Academy annual exhibition in 1888. However, in 1889 he became a member of the Society of American Artists and participated regularly in its exhibitions, showing in Academy annuals only four times thereafter: 1890, 1902, 1904, and 1905. Although Dearth was elected to full Academician in 1906, the year the Academy and the Society merged, and secured that election by presenting a work, he apparently did not choose to exhibit in the annuals held under Academy auspices.
Initially a painter of landscapes in a tonalist aesthetic, in about 1912 Dearth revolutionized his palette and began painting in brilliant, broken colors. Later, he turned to painting still lifes, often using objects from his substantial collection of Gothic, Renaissance, and Eastern artifacts as his subjects. He won several awards nationally and internationally, including a Bronze Medal at the Exposition Universelle in Paris (1900) and a Silver Medal at the Pan-American Exposition in Buffalo (1901).
In its memorial to Dearth, entered into minutes April 24, 1918, the Council noted that he "was enormously interested in color effects, and was always searching and experimenting for a better and more effective way of expressing himself."
