Simplify the following text for a Grade 6 native English-speaking person.
Original: The Johnstown Flood , otherwise known as the Great Flood of 1889 , was a major flood that happened in a city called Johnstown , Pennsylvania , in the eastern United States .
Simplified: The Johnstown Flood ( or Great Flood of 1889 as it became known locally ) occurred on May 31 , 1889 .