General fact: 1263 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Mathematical fact: 1263 is an uninteresting number.
Trivia: 1263 is an uninteresting number.
Historical date: June 16th is the day in 1972 that the largest single-site hydro-electric power project in Canada is inaugurated at Churchill Falls, Labrador.