We revised the distribution and conservation status of Sparganium L. for the Canadian Prairie Provinces (cpp ) based on herbarium voucher specimens. In the region, we recognized eight species: Sparganium americanum, S. angustifolium, S. emersum, S. eurycarpum, S. fluctuans, S. glomeratum, S. hyperboreum, and S. natans. Among these, Sparganium americanum, S. fluctuans, S. glomeratum, and S. hyperboreum are in the rare category, with conservation rankings of Critically Endangered, Vulnerable, and Endangered. Following an exhaustive herbarium specimen examination, we discovered additional collections of S. glomeratum, revealing its circumpolar distribution in North America, hence rejecting its status as introduced. In all, we were able to update the geographic distribution and rarity status of Sparganium in the cpp , especially for S. americanum and S. glomeratum. This study demonstrates that herbarium databases are powerful in identifying regions deserving conservation priority based on high diversity and high concentrations of rare or narrowly distributed species. This information facilitates the development of management strategies for the protection of unusual species assemblages.