Summary This paper analyses documents from several US archives in order to examine the controversy that raged within the US scientific community over Dayton C. Miller's ether-drift experiments. In 1925, Miller announced that his repetitions of the famous Michelson-Morley experiment had shown a slight but positive result: an ether-drift of about 10 kilometres per second. Miller's discovery triggered a long debate in the US scientific community about the validity of Einstein's relativity theories. Between 1926 and 1930 some researchers repeated the (...) Michelson-Morley experiment, but no one found the same effect as Miller had. The inability to confirm Miller's result, paired with the fact that no other ether theory existed that could compete with special relativity theory, made his result an enigmatic one. It thus remained of little interest to the scientific community until 1954, when Robert S. Shankland and three colleagues reanalysed the data and proposed that Miller's periodic fringe shift could be attributed to temperature effects. Whereas most of the scientific community readily accepted this explanation as the conclusion of the matter, some contemporary anti-relativists have contested Shankland's methodology up to now. The historical accounts of Miller's experiments provide contradictory reports of the reaction of the US scientific community and do not analyse the mechanisms of the controversy. I will address this shortcoming with an examination of private correspondence of several actors involved in these experiments between 1921 and 1955. A complex interconnection of epistemic elements, sociological factors, and personal interests played a fundamental role in the closure of this experimental controversy in the early 1930s, as well as in the reception of Shankland's reanalysis in the 1950s. (shrink)