Where did CRT come from? American legal scholars started formulating its ideas in the mid-1970s. It sprung from a field of study called Critical Legal Studies (CLS), which developed at about the same time. Both were born out of Critical Theory (CT), which was a Western-Marxist philosophy developed by scholars of the “Frankfort School,” many of whom left the Frankfort Institute for Social Research for America and Columbia University to escape Hitler’s Germany.