This document summarizes the evolution of economic development theories from the 1950s to the 1990s. It describes four main strands: 1) linear stages of growth models in the 1950s-60s, 2) structural change theories in the 1970s, 3) dependency theories in the 1970s, and 4) neoclassical, free-market theories in the 1980s-90s. It outlines the economic and political context behind each period and the major ideas that emerged, such as structuralism, import substitution, neoclassical policies, and new structuralism.