These two photos appear to be Shasta Viburnum [(Viburnum plicatum f. tomentosum 'Shasta' (Doublefile Viburnum)].
I have one very large one and another that grew when a branch of the original touched the ground and rooted. The flowers appear along the top of the branches and resemble a white dogwood from a distance. The images below are from the Missouri Botanical Gardens:
