Mary Ellen Kerr was born 25 August 1882 in Cobden Township, Union County, Illinois to Charles William and Frances Paralee (Aldridge) Kerr. She was the only child of this union although she had two older half-brothers. In her early teens, the family moved to Butler County, Missouri.
On the 1900 US census, 17-tear-old Mary E is living in Ash Hill Township, Butler County, Missouri with her parents Charles W and Francis P (sic) Kerr. (Roll: T623_843 page 8B, family #161)
Mary Ellen married Otto Alonzo McKinney on December 24th in either 1900 or 1901. They were married in Fisk, Butler County, Missouri. Their first child was Crystal McKinney, born 16 July 1904. (She married Donald Murray.) Marshall Kerr McKinney was born 03 December 1906. (Marshall Kerr McKinney died 06 September 1997 in Falls Church City, Fairfax County, Virginia, but I haven’t found anything about his adult life other than his marriage to Bertha Bertram.)
Sometime between 1907 and early 1910, Mary E and Otto relocated to Louisiana. On the 1910 US census, Mary E and her husband Otto A McKinney are living at Atlanta and Winnfield Road in Police Jury Ward 6, Winn County, Louisiana. Her mother Frances P Armstrong (now remarried) is living with her. Otto is employed as a salesman in a general store, but Mary E and her mother are managers of a hotel. Her half-brother Isacc C (sic) is staying in the hotel as is a sister-in-law of Frances P. Also listed is a servant, a cook, and fourtenn other "boarders". (Roll: T624_535, Page: 5A. Image: 677. ED: 129, family #79)
The couple did not settle long in Louisiana, as they are back in Missouri when son Robert Kenneth McKinney is born 26 March 1914 in Poplar Bluff, Butler County, Missouri. (Robert K married Carol Wade 28 June 1942 and died 24 July 1979.)
The draft registration card for Otto Alonzo McKinney shows he and his wife Daisy living at 614 Vine Street in Poplar Bluffs, Butler County, Missouri. Otto is a lawyer and clerk employed by the Missouri Pacific Railroad. Various family trees have Otto as only married once to Mary Ellen or Daisy Kerr, indicating Daisy is a nickname that Mary Ellen started using. I have no proof that Daisy is Mary Ellen rather than a second wife.
Otto A McKinney and Daisy, age 36, are living at 614 Vine Street in the City of Poplar Bluff, Butler County, Missouri at the 1920 US census. Otto is a lawyer with a general practice. Their bousehold includes the three children and two boarders. (Roll: T625_909; Page: 23B; ED: 12; Image: 387; family #257)
Otto A McKinney died 23 October 1924 in Butler County, Missouri following an automobile accident. He was buried 26 October 1924 in Woodlawn Cemetery in Poplar Bluff. (Certificate #28354)
The death of Mary Ellen in unsourced. Putting together the various pieces of data, it seems that Mary Ellen Kerr McKinney died 26 July 1961 in Colorado Springs, El Paso County, Colorado (although some records have Poplar Bluff). She was buried 31 July 1961 in Woodlawn Cemetery, Poplar Bluff, Butler County, Missouri.