After the war, Confederate states were readmitted to the Congress during the Reconstruction era, after each ratified the 13th Amendment to the U.S. Constitution outlawing slavery. "Lost Cause" ideology was an idealized view of the Confederacy, valiantly fighting for a just cause. It emerged in the decades after the war among former Confederate generals and politicians, as well as organizations such as the United Daughters of the Confederacy and the Sons of Confederate Veterans. Particularly intense periods of Lost Cause activity developed around the time of World War I, and during the Civil Rights Movement of the 1950s and 1960s in reaction to growing public support for racial equality. Lost Cause advocates sought to ensure future generations of Southern whites would continue to support white supremacist policies such as the Jim Crow laws through activities such as building prominent Confederate monuments and writing school history textbooks to paint the Confederacy in a favorable light. The modern display of Confederate flags primarily started during the 1948 presidential election when the battle flag was used by the Dixiecrats in opposition to the Civil Rights Movement and segregationists continue the practice as a rallying flag for demonstrations to the present day.