Minnesota Lt. Gov. Peggy Flanagan has frequently spoken about her family history, particularly her Native American heritage and the struggles of being raised by a single mother who relied on government assistance. Her personal story has become a central theme of her political career, including her campaign for the U.S. Senate. But newly uncovered newspaper archives reveal a far darker chapter of her family history — one involving four suspected murders, decades of confinement in state mental hospitals and an alleged threat against a federal judge. Flanagan’s maternal grandfather, John Jacob Hartmann, spent more than 30 years in Minnesota state...