I found your other posting on this family on the Werkmeister board:http://boards.ancestry.com/thread.aspx?mv=flat&m=11&...
It shows you have done a lot of background work already, with US Census and death certificates. As you noted their DC doesn't show burial place.
I searched the Land Patent database to see if they had obtained land under the Homestead Act; but, without success. I also searched for their presence in other family trees.
Could this be son Fred's gravestone?http://nebraskagravestones.org/view.php?id=120679
--You can check for others if you haven't already found this site.
Corrections to the other's post:
The 1910 Census of Butterfly, Stanton Co, NE
Fritz age 51(1858/1859), immigrated in 1871(not 1811)/naturalized. They were identified as having been married 22 years (1887/1888).
The 1920 Census of Burnett, Antelope Co, NE
Fritz "Weirkmeister" (as transcribed), age 61, immigrated in 1871/"Pa"
--"Pa" on the census stands for "Papers" meaning the person had filed their Declaration of Intention to become a citizen. It DOES NOT mean Pending Papers or Pending Application. The other poster continuously states this and is continuously in error. The instructions to the eumerators identified this to be used.
Under the paragraph of "How to Start Research" this is explained.
---In the instructions to the enumerators is found, as example for the 1900 Census: http://usa.ipums.org/usa/voliii/inst1900.shtml
-----#151. Column 18. Naturalization.—If the persons is a native of the United States, leave the column blank. If he was born abroad, and has taken no steps toward becoming an American citizen, write "Al" (for alien). If he has declared his intention to become an American citizen and taken out his "first" papers, write "Pa" (for papers). If he has become a full citizen by taking out second or final papers of naturalization, write "Na" (for naturalized).
The 1930 Census of Valley, Hayes Co, NE
The last name is written and transcribed as "Workmeister." In this census Frank is shown as first marriage at age 29 and Hanna age 21. This would again put their marriage about 1887/1888. But, you may have already found their marriage location and date.