How Did We Can? is an online exhibition curated by the National Agricultural Library (NAL) that "document[s] the progression of canning practices in the United States during the 20th century." The exhibit draws on NAL collection materials including books, articles, reports, and a multitude of images. The exhibition has five sections: Canning techniques; Consequences of improper canning; Evolution of canning equipment; Canning through the world wars; and Home canning: post World War II to present. Some of the most interesting materials explore disasters that can occur during canning. The page on oven canning, which was a popular method prior to World War II, did not require a water bath and did not heat up the kitchen as much. Oven canning was deemed unsafe in the mid-1940s, and the page features images showing shrapnel from jars that broke in the oven, and even a blown-off oven door. More horrors can be found in the Consequences of improper canning section, from split cans to botulism outbreaks. For twenty-first century canners, the full text of the 2015 edition of the USDA's Complete Guide to Home Canning is provided.