The Office of Communications in the US Department of Agriculture’s Agricultural Research Office has made its searchable collection of photographs available online.  The images are included in categories such as animals, lab research, crops, food, illustrations and other digital assets.  The images are free of copyright and are in the public domain; however, the website rights statement notes that images may not be used in a way that would be construed as endorsement by the USDA.  This collection could be helpful to the collections of smaller museums such as the Bayer Museum of Agriculture, but the museum would need to take care to abide by the policy regarding use and endorsement.