The hydrodynamic response of materials under extreme conditions of pressure, temperature, and strain is dependent on the equation of state of the matter in all its states of existence. The Trinity plutonium implosion device development required the Los Alamos physics and engineering research community to advance the understanding of equations of state further and faster than ever before. The unpredicted high yield from the Trinity fission device explosion and the push to design the “Super” thermonuclear device initiated 75 years of unprecedented research and technological progress in equation of state development. This paper describes the progress made on equation of state development during and since the Manhattan Project at Los Alamos.