Okay!!! It looks like Evelyn Florence Brown was the daughter of Oliver Deemar Brown and Anna
JAY. (an online tree)
Further searching shows that Anna Jay was married to an Albert Trusty and a Ralph Wilson before she married Oliver D Brown.
1900 Census: Forbes Precinct, Pennington, SD
https://www.familysearch.org/ark:/61903/1:1:MMRD-QCM1910 Census: Cherry County, NE (includes daughters, Rose and Eva, from previous marriage)
https://www.familysearch.org/ark:/61903/1:1:MLWY-1RB1920 Census: Sheridan County, NE
https://www.familysearch.org/ark:/61903/1:1:MC2M-T6TO Deemar Brown/Anna
children: Evelyn Brown, 0, b. NE
Ralph Wilson, 11, b. NE
Lorena Wilson, 9, b. NE
Bud Wilson, 2, b. NE
1920 Census: Pennington, SD
Albert Trusty with daughters, Rose Hopperton and Eva Trusty
https://www.familysearch.org/ark:/61903/1:1:M6JV-QWS1925 South Dakota State Census: Pennington
Albert H Trusty states he is widowed and that his wife was Anna Jay
1930 Census: Pennington county, SD
https://www.familysearch.org/ark:/61903/1:1:XQVN-G131935 South Dakota State Census: Pennington
https://www.familysearch.org/ark:/61903/1:1:MV4F-F5FOliver D Brown, age, 60; b. KS
Maiden name of wife:
JAYYear of marriage: 1918
1940 Census: Rapid City, Pennington, SD Oliver D Brown/Anna
https://www.familysearch.org/ark:/61903/1:1:V191-TPB