A sample of William's signature taken from his military registration card, 1918.
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We learned from William's military registration card that he married a girl named May somewhen before 1918,

See Richard's Military Registration Card from 1918
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We can see William at the 1920 census living at Spokane Washington with his parents-in-law and his wife.
Vickers Thomas S Head 75
Vickers Abbie H Wife 69
Holloway William J Son-in-law 38
Holloway May L daughter 30
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Name: William James Holloway
Death date: 02 Aug 1944
Death place: Spokane, Spokane, Washington
Gender: Male
Race or color (on document):
Age at death: 62 years 11 months 19 days
Estimated birth year: 1882
Birth date:
Birth place:
Marital status: Married
Spouse name: May Louise
Father name: Richard Holloway
Father birth place:
Mother name: Emily Knibbs
Mother birth place:
Occupation:
Street address:
Residence:
Cemetery name:
Burial place:
Burial date:
Additional relatives:
Film number: 2032394
Digital GS number: 4225028
Image number: 190
Reference number: 1141
Collection: Washington Death Certificates, 1907-1960

I believe May's surname was Vickers - it was not easy to read in the census returns.