Crataegus spes-aestatum J. B. Phipps is described as a new species from Missouri and Illinois. It is critically compared to C. dawsoniana Sargent, to which it keys out in the article where that species was published, and which is here lectotypified. Also, lectotypes for the following new combinations or status from the Missouri Crataegus flora are designated: C. collina Chapman var. hirtiflora (Sargent) J. B. Phipps, C. crus-galli L. var. regalis (Beadle) J. B. Phipps, C. pruinosa (H. L. Wendland) K. Koch var. magnifolia (Sargent) J. B. Phipps, C. reverchonii Sargent var. palmeri (Sargent) J. B. Phipps, C. viridis L. var. glabriuscula (Sargent) J. B. Phipps, and C. viridis L. var. nitens (Sargent) J. B. Phipps. In addition, lectotypes are designated for the varietal basionyms C. hirtiflora Sargent, C. regalis Beadle, C. magnifolia Sargent, C. palmeri Sargent, and C. glabriuscula Sargent, as well as for several of the species names involved, C. collina Chapman, Mespilus pruinosa H. L. Wendland, and C. reverchonii Sargent. Also, a lectotype and epitype for C. berberifolia Torrey & A. Gray, a species with a Missouri variety, are indicated.