In 1920 the Clark Family was living in Tacoma Ward 6, Pierce Co., WA.
William W. Clark, b. England, 31, immigrated 1893, naturalized, laborer box factory.
Martha, wife, b. Canada, 29, imm 1901, naturalized.
Shelby, son, b. WA, 9.
In 1930 the family was living in Anacortes, Skagit Co., WA.
Walter Clark, b. England, 41, marr @ 21, immigrated 1894, alien, painter interior decorator.
Martha, wife, b. Canada, 39, marr @ 19, immigrated 1902, alien.
Shelby, b. WA, 19, single.
A Martha Clark b. 1 Nov 1891, Last Residence Seattle, King Co. Died Oct 1873. Her soc. sec. # was assigned in WA in 1973. Source: Social Security Death Index, Ancestry.
You won't know if this was your Martha until you request a copy of this Martha's obituary. You can request one at no charge from the Washington State Library, sos.wa.gov/library/Genealogy.aspx .
I didn't find any death info for William/Walter.
A Shelby W. Clark b. abt. 1911, REsidence=Mt. Vernon died 18 July 1992, Mt. Vernon, Skagit Co. per death cert #027376. Source: Washington Death INdex 1940-96, Ancestry.
A Shelby W. Clark, b. 22 Nov 1910, Last Residence=Mt. Vernon, Skagit Co. died 18 July 1992. His soc. sec. # was assigned in WA before 1951. Source: Social Security Death INdex, Ancestry.
You can request a copy of his obituary from the Washington State Library (see above). Successful Searching!