The Lounsbury Musgrove Funeral Home (Eugene) records show:
SMITH, Mary Elta, age 81 years, widow
born Blue Island, Illinois
died 7 Aug 1918, Eugene
father Leonard SCOTT born Virginia
mother (no information given)
paid by C.C. SMITH, 306 Pearl St
Book 2, page 143
That IOOF cemetery is usually called the Pioneer Cemetery these days.A listing from it shows in plot 605:
SMITH, Mary E., died 9 Aug 1918, age 82
and in the same plot:
SMITH, Christopher C., 8 Apr 1860 - 22 Sep 1925
The Oregon Death Index says:
Name: Smith, Mary Etta
Death Date: 07 Aug 1918
Certificate No.: 229
Name: Smith, Christopher Columbus
Death Date: 22 Sep 1925
Certificate No.: 356
In the 1910 census I see Mary SMITH at 302 High Street, Eugene, a widow, age 65, born Illinois, father born Virginia, mother born Kentucky,
son Christopher SMITH, age 48, a widower, born Illinois,
grandson Yale SMITH, age 12, born Iowa
I see Erastus F. SMITH, wife Mary, son Christopher, and several other children in the 1880 census of Hampton, Franklin county, Iowa.
I see a Mary E. SMITH, a widow, and son Chris in the 1900 census of Hampton, Franklin co, Iowa.Their birth places are correct for the people being sought, but their ages are not quite right.
I don't see Erastus SMITH in any Lane county cemetery records, or the Oregon Death Index, or the index to Eugene newspaper obituaries 1864-1902.
My guess (and it's a complete guess) is Erastus died in Franklin county, Iowa between 1880 and 1900.