Through findagrave.com, I found my great great grandmother,
as well as her brother, Martin
and Martin's wife, Christine.
All three of them are buried in Warren, Pennsylvania, in the Oakland Cemetery, pictured here.
Update: 6/21/12 It's possible the grave marker for Annie Anderson is not our family member. I've ordered death certificates for the two Anna Andersons from Warren County, PA, who died in 1913 and 1916 and then we'll know for sure.