The surname was variously spelled Mather/Marther/Marthar.
The 1900 census shows Mary Lepper Mather living with her son Jacob Marthar (sic), he is single, Mary is widowed. Living with them is his nephew, William Davis, who was raised by them after the divorce of Jacob's sister Elizabeth Mather-Davis Walrod from Marion Clinton Davis.

Also enumerated are an adopted son and daughter: Henry Marthar, b. Dec. 1883, and Ida Marthar, b. Dec. 1886. Both born in Iowa to parents born unknown. Ida's son Don Rex (spoke by phone 6 June 2013) states their original surname was Denton, they were not related to the Mathers. Their mother had died and the father couldn't care for them. They had 2 older brothers, Jack and Oscar, who stayed with the father and settled later in Washington. Don does not know the parents first names but there is a Denton history that relates the story - of which he does not own a copy.

The 1920 census states their father was b. in Nebraska.

Ida married John Rex, they are buried in Mount Hope cemetery, Watertown, Codington Co., SD, along with Henry- now spelled Marther- who did not marry. John and Ida had 11 children.
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Although nothing came down in the family about his being married I do find three:

Jacob Marthar in the Iowa, Marriage Records, 1880-1937:

Name: Jacob Marthar
Birth Year: abt 1855
Gender: Male
Marriage Age: 26
Residence: Welton, Clinton co.
Occupation: Farmer
Marriage Date: 8 Feb 1881
Father: Smith Marthar
Mother: Mary Leper (sic)
Spouse: Mary J Walrod
Age: 26
Bride's residence: Clinton co.
Bride's father: Jonas Walrod
Bride's mother: Catherine Ames (?) (poss. Aumes)
Marriage at: Maquoketa, Jackson co.
By S. F. Milikan, Pas. Cong. ch.
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The 1885 Iowa State Census enumerates him in his mother's household as single.
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Lucy Ricker in the Iowa, Select Marriages Index, 1758-1996

Name: Lucy Ricker
Gender: Female
Race: White
Birth Date: 1876
Birth Place: Jefferson, IA.
Marriage Date: 22 Dec 1900
Marriage Place: Marion, Linn, IA.
Marriage Age: 24
Father: John Ricker
Mother: Minerva Wood
Spouse: J.S. Marthar

NOTE: SECOND marriage for both.
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Luccy (sic) V Ricker in the 1900 United States Federal Census-

Name: Luccy V Ricker
Age: 24
Birth Date: Jan 1876
Birthplace: Iowa
Home in 1900: Monmouth, Jackson, Iowa
Race: White
Gender: Female
Relation to Head of House: Daughter
Marital Status: Single
Father's Birthplace: Germany
Mother's name: Marnervy Ricker
Mother's Birthplace: Iowa

Household Members:
Name Age
Marnervy Ricker 55
Luccy V Ricker 24
Lous (sic) L Ricker 22
Ruth M McLain 4 (g-dau)

Mother- Marnervy Ricker
[Minerva Ricker]
Age: 55
Birth Date: Jul 1844
Birthplace: Iowa
Home in 1900: Monmouth, Jackson, Iowa
Race: White
Gender: Female
Relation to Head of House: Head
Marital Status: Widowed
Father's Birthplace: Kentucky
Mother's Birthplace: Indiana
Mother: number of living children: 5
Mother: How many children: 8
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Mother:
Minerva J. Ricker
Find A Grave Memorial# 6436908
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1910 United States Federal Census for Jacob S. Marther

Jacob A Marther
[Jacob S Marthar]
Age in 1910: 54
Birth Year: abt 1856
Birthplace: Iowa
Home in 1910: Cedar, Calhoun, Iowa
Race: White
Gender: Male
Relation to Head of House: Head
Marital Status: Married
Spouse's Name: Nora Marther
Father's Birthplace: Pennsylvania
Mother's Birthplace: Pennsylvania
Native Tongue: English
Occupation: Laborer
Industry: Odd Jobs
Employer, Employee or Other: Wage Earner
Home Owned or Rented: Own
Home Free or Mortgaged: Mortgaged
Farm or House: House
Able to Read: Yes
Able to Write: Yes
Years Married: 6
Out of Work: N
Number of weeks out of work: 0

Household Members:
Name Age
Jacob A Marther 54
Nora Marther 36

A third marriage for both of them, she reported one child, living.
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NOTE: No spouse is buried beside Jacob.

Member: Kent Gebhard