List all state classes when successors were formally installed on June 22, 1868.
CREATE TABLE "table1_2417340_3" (
  "state_class" text,
  "vacator" text,
  "reason_for_change" text,
  "successor" text,
  "date_of_successors_formal_installation" text
);
SELECT "state_class" FROM "table1_2417340_3" WHERE "date_of_successors_formal_installation"='June 22, 1868';