Can not find William Burnham in the 1840 Iowa Territory census but the
following is how they are listed in the 1850 Delaware Co. census.
Notice how the last names are spelled.
Iowa, Delaware County, Dist No 7, 28 Nov 1850, page 344A,
Dwelling 139, Family 142, lines 5,6 & 7.
Wm Burham 61 M Farmer Vermont
Sarah Burnham 49 F Pa
Samuel Burnham 18 M Ohio
Apple Valley, CA