Map of the Great Epizootic, 1872-1873 (ArcGIS)

Over the course of 50 weeks, an outbreak of what was believed to be equine influenza spread from Toronto to nearly every major city in Canada and the United States, infecting an enormous population of urban horses. The disease also infected horses in Mexico and other parts of Latin America.

Nineteenth-century cities in Canada and the US were filled with horses. Equine labour provided the power for intra-urban transportation and shipping. They pulled streetcars, delivered goods, and even powered machinery.

In 1872-73, cities in Canada and the US were connected by an expanding network of railways. The Grand Trunk spanned the most populous provinces of Canada and the Union Pacific recently connected the Atlantic and Pacific urban centres of the US.

Railways sped the Great Epizootic across the continent, linking the bodies of horses in Toronto to nearly every city in Canada and the US.

This is a map of the spread of the 1872-73 Great Epizootic. It also displays the approximate railway networks in Canada and the US. Each point on the map documents when the disease was first reported to have arrived in that city. Click on the points for details and source information about the arrival of the disease in each city. Use the timeline at the bottom to see how the epizootic spread over time week-by-week.