A native of East Liberty, Pennsylvania near Pittsburgh, William Sonntag was a landscape painter associated with the Hudson River School. He is best remembered for his romantic depictions of the American wilderness. From the early 1840s to the mid 1850s, he had a studio in Cincinnati and made numerous painting trips in the Ohio River Valley and into the mountains of West Virginia and Kentucky. His style of grand, sweeping vistas, and dramatic renderings was much influenced by Thomas Cole.

Sonntag's work first gained popularity because of their positive reception in the Western Art Union shows. In 1853, he first traveled to Europe, and returned in 1855 for a year's study in Florence, Italy. Upon his return, he settled in New York City and joined the National Academy of Design, where he exhibited his works for forty years. During that time he made frequent visits to the Catskill and White Mountains. His mature works of the 1860s and 1870s identify him with the Hudson River school of landscape painters and the Luminist branch of that school, in particular.

"October in New Hampshire, Near the Foot of Mount Washington" is an outstanding example of Sonntag's finest work from his best period. Here Sonntag calls into play all the grandeur associated with the father of the Hudson River School, Thomas Cole, but expands on those ideals by emphasizing both the details and the atmospherics of the scene. From 1863-1865, Sonntag affixed his name to the register at the Crawford House in North Conway, New Hampshire, along with many other great artists of the era including J.F. Cropsey, S.R. Gifford, Winslow Homer, John Kensett, and more.

A romantic and a naturalistic painter of his surroundings, Sonntag was an Associate (1860) and Academician (1861) at the National Academy of Design and a member American Water Color Society, the Artists Fund Society and the American Art Union. His work is represented in the permanent collections of the Metropolitan Museum of Art; Corcoran Gallery of Art; Peabody Institute; Berkshire Museum; Brooklyn Museum; Chrysler Museum; the Fogg Museum; Harvard University; Vassar College Art Gallery; Cincinnati Art Museum; Los Angeles County Museum; The White House, among others.

Sonntag died in New York City in 1900 one of America’s most revered landscape painters.