Simplify the following text for a Grade 6 native English-speaking person.
Original: Graham had missions in London , which lasted 12 weeks , and a New York City mission in Madison Square Garden , in 1957 , which ran nightly for 16 weeks .
Simplified: Graham had missions in both London and the Madison Square Garden in 1957 . The London mission lasted 12 weeks and the New York mission was about 16 weeks .