I have not identified the parents of Helen McMAHON McClarence, my G-Aunt. I have only found her in 2 census years so far: 1910 (McMahon)and 1920 (McCLARENCE) in Chicago, Cook, Illinois. Both census note her born in about 1882 in WI - Father born in NY - Mother born in English speaking Canada. She was b. 9 Oct 1882 and died in Chicago on 21 July 1937. Her parents names are not listed on her death certificate. She was widowed in March 1925 when her husband, John J. McCLARENCE, was run over by a train. She and John had 1 child - Richard Francis McCLARENCE. I do think Helen was related to your McMAHONs in that she attended Elizabeth (Starr) McMahon's funeral ... but she doesn't appear to be one of John and Elizabeth's 10 children. I hope this helps you out in some way. I would really appreciate your passing on the information if you come across her name in your research.
Diane - email@example.com