The CAPM emerged independently from four researchers in about 1964

Evidence

Although Sharpe did not know it at first, a model essentially the same as his Capital Asset Pricing Model was being developed at about the same time by an operations researcher namedJack Treynor. Very similar models were being developed by John Lintner at the Harvard Business School economist (Lintner 1965a,b) and byJan Mossin at the Norwegian School of Economics and Business Administration (Mossin 1966). — Donald MacKenzie, An Engine, Not a Camera, 252