Vermilion River Observatory was a University of Illinois radio astronomy facility near Danville that operated from 1959 to 1984. Built around an innovative 400-foot parabolic reflector shaped into the landscape, it surveyed much of the northern sky and produced a catalog of radio sources, identifying more than 1,000 extragalactic objects, ionized hydrogen regions in the Milky Way, and two supernova remnants. Its most famous discovery, VRO 42.22.01, became the prototype for BL Lacertae objects. A later steerable dish expanded its research and joined very long baseline interferometry. Interference concerns at its observing frequency also helped keep UHF Channel 37 off the air in the United States.

Belgium, Illinois · USA