General fact: 305 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Mathematical fact: 305 is an hexagonal prism number.
Trivia: 305 is a boring number.
Historical date: October 31st is the day in 1963 that an explosion at the Indiana State Fair Coliseum (now Pepsi Coliseum) in Indianapolis kills 74 people during an ice skating show.