Hi Diana, I thought I had posted this reply in Sept. but it looks like maybe it didn't go through.
I found William and Mary and their family on the 1880 Columbia, Washington Census. William was b. IL, abt. 1836, and a farmer; Mary C. b. IN, abt. 1845; Nancy J. b. OR, abt. 1862; Perry P. b. OR, abt. 1864; Thomas I. b. OR abt. 1866; Marsha E. b. OR abt. 1868; William R. b. Wash. Territory, abt. 1869; Milton R. b. W. T. abt. 1870; Florence b. W. T. abt. 1873; Esland or Esbon (son) b. W. T. abt. 1875 and Elsie May b. W. T. abt. 1877. This family was in WA EARLY!
Nancy Jane Marlatt married William Maurice Cattron 8 Jan. 1882. Nancy was b. 17 Feb 1862, Independence, OR. Parents=William Marlatt & Mary Catherine Kenoyer. Source: Family Data Collection-Individual Records. Of course you should get a copy of the marriage license for a double-check.
Then they appeared in the 1883 Wash.Territorial, Columbia County Census. Marlatt, W., b. IL, male, abt. 1836; M. C., 38, fem, b. IL; P. P. 19, male, b. IN; T. L., 17, male, b. OR; M. A., 14 fem, b. OR; W. R. 12, male, b. Wash. Terr.; J. M., 10, male, W.T.; F, 8, fem, b. W. T.; Esbon, 5, male, b. W. T.; E, 3, fem, b. W. T.
They were there according to the 1887 Wash. Territorial, Columbia County Census. William was still a farmer.
Peter Perry Marlatt married Sadie Broyls 1887. Peter was b. 11 Sep 1863, Lyon Co., OR. Parents William Marlatt & Mary Catherine Kenoyer. Peter died Oct 1898, Albion, Whitman Co., WA. Source: Family Data Collection-Individual Records. You should get copies of marriage & death certs to verify.
Thomas Lincoln Marlatt married Martha Scroggins. His parents=William Marlatt & Mary Catherine Kenoyer. He was b. 1 Sep 1865, Lyon Co., OR. Source: Family Data Collection-Individual Records. Should be verified.
They were still there according to the 1889 Wash. Territorial, Columbia County Census. I THINK William had died by 1889 because he's not listed in this Census. M. C. Marlatt, 44, b. IN, female; Ella, 21, b. OR; William, 20, born Wash. Terr; Milton, 20 b. W. T.; Florence, 16, b. W. T.; Esbon, 11, b. W. T.; Essie, 7, b. W. T.; P. P. 25, b. OR, farmer; S. C. 19, b. OR and ?, one year, b. W. T.
JOhn Milton Marlatt married Ruby Estella Shaw. His parents were William Marlatt & Mary Catherine Kenoyer. John was b. 23 Jan. 1871, Dayton, Columbia Co., WA. He was married 22 Jan 1898, Walla Walla, Walla Walla Co., WA. He died 1 March 1945, Freewater, OR. Source: Family Data Collection-Individual Records. Should be verified.
Elsie b. 6 Nov 6 1879, IN. Parents William Marlatt & Mary Catherine Kenoyer. Source: Family Data Collection-Births. Should be verified.
Florence m. Franklin Andrew Brown 10 June 1895, Colfax, Whitman Co., WA. Her parents were William Marlatt & Mary Catherine Kenoyer. She was b. 6 Dec 1873, Dayton, Columbia Co., WA. She d. 29 March 1930, Jacksonville, OR. Source: Family Data Collection-Individual Records. Should be verified.
In 1900 Mary and some of the children are living in Big Eddy, Nez Perce, ID. Mary, head, b. Feb. 1845, widow, farmer; William, b. Mar 1869, single, b. WA, farm laborer; Elsa, b. Nov 1879, WA, single, dressmaker; Lora [Lois?], granddau., b. March 1888, OR; and Roy, grandson, b. OR Feb 1890. Even though this Census says that Mary is a widow I think she was divorced.
The 1910 Gifford, Nez Perce, ID Census shows William Marlatt, father law, b. IL, abt. 1836 living with the Spivey family. Alfred L. Sprivey, head household, b. MO, 47, farmer; Elsie M., wife, b. WA 30. Elsie had given birth to 4 children but only 3 are living in 1910. Hattie, b. ID 7; Lawrene (son), b. ID 4 and Baby Spivey (son), b. ID 8 mos.
1900 Warm Springs, Grant Co., OR Census Thomas Marlatt, head, b. Sept. 1866, OR, single, farmer.
I'd check www.interment.net for Columbia County cemeteries. Good Luck!