Mrs. Anna Sophia Simmons
Died: 29 May 1925, Pope Co. MN
Source: MN Death Index 1908-2002
Irvin E. Simmons
Born: 28 March 1872
Mother's Maiden Name: Cohen, b. MN
Died: 14 Aug 1965, Pope Co. MN
Source: same as above
I didn't find where they were buried in Ancestry and FamilySearch.
You can contact the Pope County Historical Society, http://popecountymuseum.wordpress.com/research-at-pchs/
who has newspapers back to 1871. Generally where a person was buried will be in their obituary. They also have cemetery lists which might mean they have inventoried their cemeteries. Successful Searching!