Since the nineteenth century, the US Naval Observatory (USNO) has contributed to the science of relativity and also benefited from it. Albert Michelson received USNO support and employment before going on to undertake the Michelson-Morley experiment. USNO first flew atomic clocks around the world as a test of relativity. USNO staff have written articles and a textbook on relativity, and a pedagogical explanation of why curved space-time causes an apple to fall is provided. Two recent tests of Einstein's equivalence principle (EEP) are described, and a section in memory of Dr. Gernot Winkler is included at the end of this work.