| | Department of Agriculture is established in 1862 by Abraham Lincoln. |
| | A variety of National Collections of seeds, fungi, plants, insects and mites, nematodes and animal parasites are started which are eventually housed at Beltsville. These collections continue to serve as unique repositories and references for the scientific community. |
| | The first Agriculture building is constructed in 1867 on the Mall just north of today's USDA complex.
The germ theory of disease is verified when bacteria and insects are shown to spread diseases to plants by Erwin Smith and Merton Waite |
| | The Experimental Farm and the Experimental Garden are established on the Mall in Washington, DC north and west of the Washington Monument. In 1871, a large conservatory and greenhouses are constructed adjacent to the Agriculture building. |
| | Wilbur Atwater devises an improved type of "bomb" calorimeter that measures the energy content of protein, carbohydrate and fat. |
| | The Veterinary Experiment Station is established in 1863 in order to move the farm animals off the Mall. This Station is first located between 18th Street and Benning Rd. in Washington, DC and is expanded and relocated in 1897 to Bethesda, MD. The Bethesda site is where the Bethesda-Chevy Chase Recreation Area is now located. |
| | The first biological control of a plant pest succeeds when Charles Riley imports Vedalia beetles from Australia to control scale on citrus. |
| | The Experimental Farm and Experimental Garden are expanded and relocated in 1903 to the newly established Arlington Farms Experiment Station in Arlington, VA. This site is where the Pentagon is now located. |
| | USDA purchased Walnut Grange plantation in Beltsville, MD. Dairy and Animal Husbandry activities were relocated to this site in 1910. This land was originally owned by Thomas Snowden and was given to his daughter Mary when she married John Herbert of Walnut Grange, VA. The house was built around 1790. |
| | The carrier of cattle tick fever is discovered, showing that a disease-producing microorganism could be transmitted by an insect from one animal to another. This laid the basis for the eradication of cattle tick fever in 1943.
The government human nutrition research conducted in Middletown, CT is transferred in 1906 to USDA in Washington, DC. |