Smithfield Cemetery
Allamakee County, Iowa

Find A Grave has a photo of this gravestone listed as B. D. Clark that shows it cleaned-up some. At the very top of the stone in that photo appears a name that looks like Maria. The rest of that photo shows:

Dau. Of B. D. & E. A. Clark, died Apr. 16, 1874, Aged 21 ys, 7 Mos and 16 Ds.