Question: The Sir Ralph Abercromby is the only structure remaining in St Peter's Field after cavalry charged into a crowd had gathered to demand the reform of what? 
Sentence (from "Peterloo Massacre"): The Peterloo Massacre occurred at St Peter's Field, Manchester, England, on 16 August 1819, when cavalry charged into a crowd of 60,000–80,000 who had gathered to demand the reform of parliamentary representation.
Relevant evidence: Yes