Juliette Magill was born in Middletown, Connecticut, to Frances Wolcott Magill and her second husband, Arthur William Magill. Her mother's ancestors, some of whom helped found Windsor, Connecticut, in 1636, included Roger Wolcott, a colonial governor and judge, and Alexander Wolcott, leader of Connecticut's Republican party. Well educated, Juliette was tutored in Latin and other languages by her mother and young uncle, Alexander Wolcott, and briefly attended a boarding school in New Haven, Connecticut, and Emma Willard's school in Troy, New York.
Wolcott, who had moved to Chicago in 1810, probably introduced Juliette to John H. Kinzie, son of fur trader John Kinzie. They married in 1830 and moved to Detroit and then Fort Winnebago, a new trading post at the crucial portage between the Fox and Wisconsin rivers. Her husband was an Indian sub-agent to the Ho-Chunk nation (Winnebago people), assigned to this area that connected the Great Lakes/St. Lawrence and Mississippi watersheds.
After the treaty ending the
Sauk War of 1832 forced the Winnebago to move west of the Mississippi River, the Kinzies left the area that would later become Wisconsin and in July 1833 moved to Chicago in the relatively new state of Illinois to join Kinzie's widowed mother and siblings. The Kinzie family was involved in Chicago's civic and social development throughout the 19th century. Active in the Episcopal church, Juliette Kinzie helped found St. James Church, now the oldest Episcopal congregation in the city, and since 1955 the cathedral for the Diocese of Chicago. The Kinzies also helped found St. Luke's Hospital and the Chicago Historical Society (now the Chicago History Museum).
Kinzie died while vacationing in Amagansett, New York, Long Island, in 1870, after a druggist accidentally substituted morphine for the quinine she ordered.