Millions of Americans will celebrate 4/20 as a marijuana-related holiday whose origin I don’t understand at all. Others will remark grimly that it is Hitler’s birthday. But you might also want to note the anniversary of an important piece of anti-terrorism legislation, the Ku Klux Klan Act, passed by the Republican 42nd Congress in 1871 and signed by President Grant. The law, which banned the Klan, was overturned by the Supreme Court over a decade later.