After the fall of South Vietnam in April 1975, hundreds of thousands of refugees, called boat people, fled Vietnam and adjacent nations. According to Canadian immigration historian Valerie Knowles, from 1979 to 1980 Canada admitted an estimated 60,000 of these refugees, "most of whom had endured several days in small, leaky boats, prey to vicious pirate attacks, before ending up in squalid camps". Knowles says it was the highest number of boat people accepted by any nation, including the United States, during that period. The boat people constituted 25% of all newcomers admitted to Canada from 1978 to 1981. This created a substantial Vietnamese community in Canada, concentrated especially in Montreal, Vancouver, and Toronto.