In early March 1919, U.S. public health officials investigated a cluster of paralytic illnesses traced to home-canned ham. Medical and public-health reports from the period identify this event as the first recorded outbreak of foodborne botulism in the United States, occurring in the context of growing awareness of food preservation risks and nascent national public-health surveillance. Background By the 1910s, home canning and commercial canning were common in the United States. Canning technology and sanitation varied widely; low-acid foods such as meats and vegetables require higher temperatures and pressure processing to inactivate spores of certain bacteria. Clostridium botulinum, the bacterium that produces botulinum neurotoxin under anaerobic conditions, had been identified in the late 19th and early 20th centuries, and its association with foodborne paralysis was becoming clearer through laboratory and clinical work in Europe and North America. The 1919 outbreak Contemporary accounts and later public-health summaries report that in March 1919 health officials documented multiple cases of severe, sometimes progressive flaccid paralysis after consumption of the same home-canned ham. Symptoms described in reports included blurred vision, difficulty speaking and swallowing, gastrointestinal upset preceding neurologic signs, and descending paralysis—features consistent with botulism. The investigation linked the illnesses epidemiologically to the contaminated ham; laboratory confirmation by modern standards (isolation of toxin or organism) was limited at the time, but the clinical pattern and food association led authorities to identify the cause as botulism. Public-health impact and response This outbreak contributed to heightened attention to canning safety for low-acid foods. Public-health messaging and later regulatory developments emphasized the need for adequate heat processing and proper sanitation in canning meat products. Over subsequent decades, improvements in commercial canning processes, adoption of pressure canners for home preservation of low-acid foods, and better laboratory methods for detecting botulinum toxin reduced the frequency of such outbreaks. Nonetheless, botulism remained a recognized hazard prompting both consumer education and regulatory action. Historical context and limitations Documentation from 1919 lacks many elements of modern outbreak investigation: laboratory assays for botulinum toxin were rudimentary or unavailable, and record keeping varied. Consequently, while this event is widely cited as the first recorded U.S. foodborne botulism outbreak, some details (exact number of cases, precise laboratory confirmation) are limited or absent in surviving reports. Later historical reviews and public-health sources have treated the March 1919 ham-associated cluster as the earliest well-documented domestic instance linking canned meat to botulism. Legacy The 1919 outbreak helped to establish the link between inadequate heat processing of low-acid canned foods and the risk of botulism, shaping public-health guidance for both home preservation and commercial canning. It stands as an early example of how clinical observation, epidemiology, and evolving laboratory science combined to identify and mitigate a foodborne threat.