Simplify the following text for a Grade 7 native English-speaking person.
Original: In 1932 the electrified District Line of the London Underground was extended to Upminster through Dagenham with stations opened as Dagenham and Heathway and today called Dagenham East and Dagenham Heathway . Dagenham East was the location of the Dagenham East rail crash in 1958 .
Simplified: Dagenham is an area of London , United Kingdom .