Over the past 35 years, Witherill's photographs have been exhibited in more than eighty-five individual and group exhibitions in museums and galleries throughout the world. His photographs represent a remarkably varied approach to the medium including landscapes, studies of pop-art, botanical studies, urban architecture and digital imaging. In 1999, Witherill was the recipient of the “Artist of the Year” award, presented by the Center for Photographic Art, Carmel, CA.
In 2000, a nationally acclaimed hard bound monograph featuring Witherill's landscape images, entitled: Orchestrating Icons, was published by LensWork Publishing. The following year, a companion monograph featuring his black & white botanical photographs, entitled: Botanical Dances, was also published.
Witherill’s photographs are maintained within many important public collections including; The United States Department of State: Art in the Embassies, Fundacióe Van Gogh d’Arles, Arles, France, The National Museum of Modern Art, Kyoto, Japan, The Everson Museum of Art, Syracuse, NY, The Asheville Art Museum, Asheville, NC, and The Monterey Museum of Art, Monterey, CA.
Since 1975, Witherill has taught photography for a variety of institutions and workshop programs throughout the United States, including the University of California, The Friends of Photography, The Oklahoma Arts Institute, and The Ansel Adams Gallery.