On April 16, 1819, 15 peaceful protestors were killed and hundreds were injured at St Peter's Field, Manchester, Lancashire, England while gathered for a meeting to discuss parliamentary reform. To break up the meeting, the cavalry charged into a crowd of approximately 60,000 to 100,000 people from both the local area and across the North West.

After the end of the Napoleonic wars in 1815, England experienced an economic slump. As a result, an increasing number of working-class people became involved in reform movements. Calls for universal male suffrage were based on the argument that allowing working-class men to vote would result in a better use of public funding, fairer taxes, decreased unemployment, and less restricted trade. The movement was led by men like Henry Hunt, who was speaking the day of the massacre. While petitions gained over 750,000 signatures in 1817, the House of Commons ignored the movement’s demands. A second economic slump in 1819 pushed the movement to mobilize with more immediacy.

The events at Peterloo were a part of this new push in the campaign. Despite the urgency of the cause, the tone of the day was one of celebration. In addition to men, women and children attended, and all were dressed in their best Sunday clothes.