420 IS THE SYMBOL NUMBER FOR MJ. ALL THIS STARTED IN 1971 SAN RAFAEL CA. SECUNDARY SCHOOL WHEN ALLEGEDLY A GROUP OF 5 STUDENTS FOUND A MAP THAT INDICATED AN SPECIFIC PLACE WHERE MJ COULD BE . THEY AGREED TO GO AFTER CLASS AT 4:20 pm AND FOUND NOTHIG. THEY ADOPTED THAT NUMBER AS A SYMBOL AND SPREAD IT . A ROCK BAND HAD THAT NUMBER (420) AS A LOGO AND 420 MJ MAGAZINE TOO. GLTA