Deansgate is one of Manchester's most historic streets. During the Roman occupation it formed the route between two river crossings, the fords of the River Medlock to the south and the River Irwell to the north. The name Deansgate probably emerged in Anglo Saxon times and applied to that section of road between the present junctions of Cateaton Street and Peter Street.
Aldport Lodge, situated just south of Peter Street, was the manor house of the old town, and that part of present day Deansgate was originally known as Aldport Lane. The present name was not adopted for this stretch until Victorian times. From this manor house Lord Strange's Royalist forces fired cannon along Aldport Lane in 1642, against the Parliamentarians, who were strongly supported by the people of Manchester. The siege of Manchester brought about some of the earliest bloodshed in the Civil War.
Land on either side of the road was used for agricultural purposes until the encroachment of urban development, which accelerated in the 1730s, around the time when Edward Byrom built a substantial quay on the River Irwell.
Quay Street was built to allow access between the quay and Aldport Lane, and was extended eastwards in 1794 to link with Mosley Street. The new street was called Peter Street, named after St Peter's church which was being constructed at that time on Mosley Street. St Peter's Square, which also took the name of the church, came into being when the church was demolished in 1906.
Well into the 19th century, this part of Manchester still bordered upon open countryside. On 16 August 1819, at St Peter's Field (just off the present day St Peter's Square), Henry Hunt addressed a meeting of 60,000 people to demand radical reform of the House of Commons.
The size of the crowd so alarmed the City Magistrates that troops were called in to disperse it. Eighteen people were reported killed and 700 injured in the resulting chaos. The incident is now remembered as the 'Peterloo Massacre', and is commemorated in a plaque located on the Free Trade Hall, which was built on the site. This event, one of the most important in the City's history, undoubtedly paved the way for the 1832 Electoral Reform Act.