American botanist, ornithologist and palaeontologist on the United States Geological Survey. From Brandon, Vermont, Frank Knowlton studied under Erza Brainerd at Middlebury College and received a BSc in 1884. At this time he was employed by the US National Museum to work on the exhibit for the Cotton Centennial Exposition in New Orleans. After the exposition he was kept on at the museum (in Washington, DC) as an assistant curator. From early on in his life, Knowlton was interested in botany and ornithology and he began to study and teach botany at Columbian University (now George Washington University). He received a PhD in 1896 and the following year became the founder of the publication Plant World of which he was the editor for a further seven years.

Knowlton was also employed on the US Geological Survey, initially as assistant to the head of palaeobotany, Lester F. Ward, and later as assistant palaeontologist and geologist (from 1907). His most important publication was a beautifully illustrated Birds of the World (1909). Knowlton was a member of the Paleontological Society and its president in 1917. He was awarded a DSc by his alma mater in 1921.

Sources:
E.W. Berry, 1927, "Frank Hall Knowlton", Science, 65: 7-8.