Hi,
I found your husband's grandfather in the 1910 census.

1910 Liberty, Barry Co., MO
Harrison, Henry Head 31 md1 12 AR TN AR Farmer (his birthplace, and the birthplace of his father and mother)
Lula B. wife 28 md1 12 6-5 MO TN MO (she was 28, married once, for 12 years, 6 children, 5 living)
Tracy L. dau 11 s MO AR MO
Clarence E. son 7 s " " "
Charles G. son 5 s " " "
Lola M. dau 2 s " " "
Lee B. son 5/12 s " " "

Using this, I found a listing for the family in Ancestry.com.

Henry was Francis Henry Harrison, b. 1879 Carroll, AR,
m. Lula B. Stewart 1898. Francis Henry Harrison was the son of Joseph Harrison, b. 1847 Carroll, Missouri,
d. 24 Jul 1936 Lebanon, Leclede Co., MO, and Louisa Baker. Joseph Harrison was the son of Benjamin Harrison
born 26 Feb 1812 in Kentucky, d. 8 Jun 1897 in Dutch Mills, Washington Co., Arkansas and Elizabeth Adkins.
He was the son of William Henry Harrison (not the president) b. 1768 VA, d. 1848 Carroll Co., MO, m. Winifred Hancock

I didn't check these out to confirm whether the line is correct, but have no reason to doubt it. I found the marriage record
of Henry and Lula and it did give her last name as Stewart. Since they were under 21, it was signed by L.M. Harrison, his
mother, and L.M. Stewart, her father, so now you also know her father's initials, which will make finding her ancestors
much easier.

There have been a lot of folks who've worked on this family, and I have seen three different sets of parents for this
William Henry Harrison b. 1768 listed over the years. The one person who we have tested in the Harrison DNA Project who is part of this family matches the line of Anthony Harrison of Over, England, that goes back to the 1500s in Cambridgeshire, but is not part of the "presidential Harrison" line. You can check it out in lineage 4 of the Harrison project at
http://www.worldfamilies.net/surnames/harrison/pats

The "James River Harrisons" are the presidential Harrison line, and they are lineage group 34.

Hope this helps!
John Harrison