I found a Mary H. MacKillip in the 1900 Cook County, IL US census listed as the superintendent of a "Balm of Gilhead Home" (unsure of first word). The location is 466 North Clark Street. Her birth dates look right and it lists her as a widow. Her parents' birth places are listed as both NY. In the 1880 US census, Mary lists her parents' birth places as both Ireland. Perhaps some research at the Chicago Historical Society will bring some more info to light.
More About Mary Henry Jones: Date born 2: Milton Junction, WI.691 Census: Jun 1880, Chicago, Cook, IL.692
Children of Mary Henry Jones and Dennis Karney McKillip are: