A map of St Peter's Field and surrounding area on 16 August 1819
The area around St Peter's Square, then known as St Peter's Field, was the site of the 1819 Peterloo Massacre. The name derives from St Peter's Church which was built in 1788-94 where the gardens are today and also gave its name to Peter Street. The church was built in the neoclassical style by the architect James Wyatt, and was once famous for its church music. It was demolished in 1907 and the Cenotaph replaced it in 1924. A stone cross (1908) commemorates the church. The square is the site for the city's Remembrance Day commemoration each year.
In the 1930s, the square was redeveloped around the construction of the Central Library and Town Hall Extension (1930–34). Plans for a rapid transit station in St Peter's Square were made in the 1970s; proposals for the abandoned Picc-Vic tunnel envisaged the construction of an underground station to serve both St Peter's and the neighbouring Albert Square. The early proposals for an on-street light rail system in Manchester revived the idea of a station in the square, and the idea was retained as the project evolved, becoming a reality when the Metrolink system opened in 1992.
In 2013, Manchester City Council approved plans for the redevelopment of the square, including the expansion of the Metrolink stop to four platforms. This coincided with the construction of the One and Two St Peter's Square buildings and the refurbishment of Manchester Central Library, both adjacent to the square.
The scheme involved using £20 million of public money, moving the Cenotaph, moving the Peace Gardens, demolishing an inter-war building to establish a new office quarter and closing Library Walk to the public. The plans were criticised as bland, unrealistic and private sector orientated rather than public orientated.
In response to the criticisms Darryl Lee, director of Mosley Street Ventures, said: "The developers have had lengthy and detailed discussions about their proposals with English Heritage and Manchester City Council, who have pronounced themselves happy with the scheme". An English Heritage spokesperson added: "Long before Century House was built, St Peter’s Square was envisaged as a grand civic space, and English Heritage feels that the Simpson scheme, taken with other developments which are under way, goes some way to realising that ambition. While we think that Century House makes a positive contribution to the conservation area, we feel that its loss is outweighed by the public benefits of the scheme."
A statue of Emmeline Pankhurst was unveiled on 14 December 2018 to commemorate 100 years since women were first allowed to vote in United Kingdom general elections.