For four centuries, dykes held back the largest tides in the world, in the Bay of Fundy region of New Brunswick and Nova Scotia. These dykes turned salt marsh into arable land and made farming possible, but by the 1940s they had fallen into disrepair. Dykeland was in danger. Against the Tides is the never-before-told story of the Maritime Marshland Rehabilitation Administration (MMRA), a federal agency created in 1948. As farmers could not afford to maintain the dykes, the MMRA stepped in to reshape the landscape and with it the communities that depended on dykeland. Agency engineers borrowed from some of the farmers’ long-standing practices, but they were so convinced of their own expertise that they sometimes disregarded local conditions, marginalizing farmers in the process. The engineers’ hubris led to construction of tidal dams that compromised a number of rivers, leaving behind environmental challenges. This book combines interviews with people from the region, archival sources, and images from the record the MMRA left behind to create a vivid, richly detailed account of the push–pull of local and expert knowledge, and the role of the state in the postwar era. Ultimately, Against the Tides is a compelling study of a distinctive landscape and the people who inhabited it that encourages us to rethink the meaning of nature.