At which university did Watson and Crick work together?

Watson and Crick worked together at the University of Cambridge.

Their collaboration took place principally at Cambridge's Cavendish Laboratory, one of the world's leading centers for experimental physics and molecular research. Francis Crick was already working in an associated Medical Research Council unit when James Watson arrived from the United States in 1951.

At the Cavendish, the two scientists combined model-building with evidence from X-ray diffraction and related chemical research to work out DNA's double-helical structure. Their breakthrough came in 1953, after months of testing models and discussing data from researchers including Rosalind Franklin, Raymond Gosling, and Maurice Wilkins at King's College London.

A common mix-up is to answer Oxford because several scientists who saw the new DNA model worked there, or Harvard because Watson later joined its faculty. Neither is the answer: the landmark partnership occurred at Cambridge, and the first Watson–Crick DNA paper appeared in Nature on 25 April 1953.