Crataegus monogyna Jacq.  
Family: Rosaceae
English hawthorn, one-seeded hawthorn
[Crataegus curvisepala auct. non Lindm., Crataegus oxyacantha var. paulii L.]
Crataegus monogyna image
from USDA Plants website  
Crataegus monogyna image
from USDA Plants website  
Crataegus monogyna image
Botanical Illustration  
Crataegus monogyna image
Botanical Illustration  
Crataegus monogyna image
Botanical Illustration