Huckle, Myron S. 1921. "Horticulture students studying tree roots." From Manuscripts, Archives, and Special Collections, Washington  State University Libraries. Retrieved 10 October 2020  (https://content.libraries.wsu.edu/digital/collection/p16866coll18/id/360).

Below are links to some useful resources that have open access/public domain images related to gardening and agriculture. Do remember, different images and websites may have different license and use policies. 

Regional Content

• Washington State University Libraries Digital Collections - WSU Libraries Digital Collections provide access to the academic and cultural heritage of Washington State and the Palouse Region.
• Washington State Library Photograph Collection, 1851-1990 - This collection consists of 5,274 images of various subjects related to Washington's history, people, geography, and economic development (1851-1990).
• University of Washington Online Special Collections - Digital collections covering a wide range of subjects pertaining to regional history.
• Whitman County (Washington) Rural Heritage Collection  - Many historical images of agriculture around the state and on the Palouse.
• Idaho State Archives / Historical Society - Collection of Idaho historic digital collections.
• Idaho Transportation Photo Collection - 30,000+ historic pictures.
• Idaho State Archives Photographs - The photograph collection includes over 500,000 images, dating from the territorial period to present day.
• The Plateau Peoples' Web Portal (Collections) -  The Plateau is a  Peoples' Web Portal collaboration between many northwestern and plains tribes and the WSU Center for Digital Scholarship and Curation. This portal serves as an extensive repository of cultural materials including many photographs. 

National and International Collections 

• Library of Congress Image Catalog - Thousands of images from the U.S. Library of Congress.
  • See also: Library of Congress Online Photo Catalog - Presents over 1,300 items with a over 4,000 images and a date range of 1824-1931.
• USDA Agriculture Research Services Image Collection - Many fantastic, and current, agriculture and horticulture images.
• USDA National Agriculture Library (NAL) Image Collection - The NAL provides many images across numerous subjects. 
  • See also: NAL "Art & Images."
• University of Nebraska Institute of Agriculture and Natural Resources - Free Food-Related Photo Sources
• New York Public Library Image Collection - Thousands of images across many subjects.
• Bio Heritage Library Photo Collection - This link provides information regarding searching the extensive BHL historic image library.
• United States Geological Survey (USGS)  - A searchable archive of thousands of USGS historic photos.
• Natural Resources Conservation Service Photos & Multimedia - A large collection of images and animations from the NRCS. 
• USGS Multimedia Library - Explore our planet through photography and imagery, including climate change and water all the way back to the 1800s when the USGS was surveying the country by horse and buggy.
• The Internet Archive (Image Collection) - Archive.org provides extensive multidisciplinary resources that includes photographs.