“In Conceptual art, the idea or concept is the most important aspect of the work.” Sol LeWitt wrote in 1967. “When an artist uses a conceptual form of art, it means that all of the planning and decisions are made beforehand, and the execution is a perfunctory affair.” Following LeWitt’s credo, Conceptual art was a pioneering international art movement in the 1960s and ’70s, which expanded the definition of art to include written instructions, absurdist performances, found object sculptures, and more. The boundary-pushing techniques of the Conceptual movement find their roots in Marcel Duchamp, who famously challenged the art world establishment by submitting an upside-down urinal to be displayed as a sculpture in 1917. In the auction market, record sales of Conceptual Art include Bruce Nauman’s Henry Moore Bound to Fail (1967) at $9.9 million, Eva Hesse’s Iterate (1967) at $4.5 million, and John Baldessari’s Quality Material.... (1967–1968) at $4.4 million. Below, discover historic works from these Conceptual artists and other landmark figures of the movement, including Joseph Beuys, Joseph Kosuth, Mel Bochner, and On Kawara.