If Dred Scott, Citizen’s United, and Florence v Burlington are the three worst decisions by the United States Supreme Court, (post here) then Korematsu v United States, Dec. 18, 1944, Plessy v Ferguson, May 18, 1896 are next in line.
In Korematsu v United States, decided Dec. 18, 1944, the Supreme Court upheld Executive Order 9066, authorizing the internment of all Americans of Japanese ancestry. Mr. Korematsu is biographed here.
Plessy v Ferguson, decided on May 18, 1896, enabled segregation. This was overruled by Brown v Bd. of Education, May 17, 1954, with the now famous observation that “separate but equal is inherently unequal.”