Tamsen Donner. For most the name conjures the ill-fated Donner party trapped in the snows of the Sierra Nevada Mountains in 1846-47. Others might know Tamsen as the stoic pioneer woman who saw her children to safety but stayed with her dying husband at the cost of her own life. For Gabrielle Burton, Tamsen's story, fascinating in its own right, had long seemed something more: the story of a woman's life writ large, one whose impossible balancing of...