United States Department of Agriculture Building, by Unknown, 1868, Smithsonian Archives - History Div, In 1862 Congress established a separate Department of Agriculture for the purpose of promoting the art of husbandry and the general diffusion of agricultural knowledge, and also for the importation and distribution of the most valuable seeds of foreign and domestic growth. The United States Department of Agriculture building was built in 1867 and razed in 1930. In 1868 a staff of 72 was able to occupy its new headquarters on the Mall..