Cunningham was born in 1873 and lived in Lake County, Indiana, near Gary. Between 1918 and 1922 her husband David and four of her children died: Isabelle, twenty-eight, Harry, twenty-three, Charles, eighteen, and Walter, thirteen. Each death was attributed to illness at the time.
Suspicion arose in 1923 when her son Walter died and a doctor who had attended more than one of the deaths refused to certify it. Arsenic was found, exhumations followed, and arsenic was found in the others. She had taken out life insurance policies on each of them.
She confessed to the five killings and was tried on one count. She was convicted in 1925 and sentenced to life imprisonment.
The case ran in the Chicago and Indiana papers as another black widow poisoning, alongside Tillie Klimek's in the same period and the same region, and the two were reported together at the time. Only one murder was tried, and the account of the other four rests on her confession and the exhumation findings.