We have a birth record for Martha Davis and she appears in the 1900 census. We have a count of children for mother Anna Horner Davis (12 children, 11 living) that is consistant. However, father James William Davis dies in 1901, and the family disperses. [2023MAY06: I question this death date, but family still disolved for 1910 census.] I find no further records regarding Martha.

In the 1938 obituary of sister Elmira Davis Allen there is no mention of Martha as a sibling. Since all the others mentioned are still living, this would seem to be a list of "survived by" - suggesting that Martha pre-deceased Elmira. (Father William and brother Joseph are similarly not mentioned.) I infer from this that Martha died sometime between the 1900 Census and Elmira's death in 1938.

For the 1920 census and beyond, mother and all children other than Martha are accounted. Unfortunately, I am unable to locate a 1910 census record for mother, Joseph, Martha, or Elbie. (1910 entry for mother Anna should include a count of children still living.)

With the common nature of the Davis name, and the lack of 1910 census info, I declare this a Brick Wall for me. A small reward for any help.