Beaubien first visited Fort Dearborn, which later became the heart of downtown Chicago, shortly after its construction in 1804, but did not buy property there until 1812.
 In April 1812, he left with his new wife Josette La Framboise and her metis family, all of whom returned to Milwaukee after unfriendly Winnebago killed and scalped several Caucasian settlers on an outlying farm, in what turned out to be a prelude of the Fort Dearborn Massacre of August 15, 1812.
Fellow trader John Kinzie, a friend of the fort's commander Nathan Heald, moved his family into the fort, and in early August warned Heald against obeying an evacuation order after the War of 1812 began; Heald's disregard of that advice and compliance with the order to move to Fort Wayne led to the massacre.
Meanwhile, in June, Kinzie had killed interpreter Jean LaLime who was a member of a rival faction within the fort, and fled to Milwaukee, where he was greeted with suspicion and found those Indians both anti-American and planning to join western Indians under the direction of British trader Robert Dickson at Green Bay and war against the Americans.
After returning to Chicago and failing to convince commander Heald to stay in the fort, Kinzie ultimately enlisted fellow trader Alexander Robinson, who eventually managed to evacuate some survivors to Grand River and Detroit.

Beaubien, Robinson and Bailly continued to trade during the conflict, supplied by Dickson rather than his American competitors.
In January 1814, an American expedition led by Robert Forsyth (John Kinzie's half-brother) captured Bailly and three other traders at St. Joseph.
John Kinzie then traveled to St. Joseph, where he convinced several native American leaders to travel to Greenville, Ohio to attend an American peace conference which led to the Treaty of Greenville (1814), although other Native leaders (particularly Main Poc refused)
Beaubien first visited Fort Dearborn, which later became the heart of downtown Chicago, shortly after its construction in 1804, but did not buy property there until 1812.  In April 1812, he left with his new wife Josette La Framboise and her metis family, all of whom returned to Milwaukee after unfriendly Winnebago killed and scalped several Caucasian settlers on an outlying farm, in what turned out to be a prelude of the Fort Dearborn Massacre of August 15, 1812. Fellow trader John Kinzie, a friend of the fort's commander Nathan Heald, moved his family into the fort, and in early August warned Heald against obeying an evacuation order after the War of 1812 began; Heald's disregard of that advice and compliance with the order to move to Fort Wayne led to the massacre. Meanwhile, in June, Kinzie had killed interpreter Jean LaLime who was a member of a rival faction within the fort, and fled to Milwaukee, where he was greeted with suspicion and found those Indians both anti-American and planning to join western Indians under the direction of British trader Robert Dickson at Green Bay and war against the Americans. After returning to Chicago and failing to convince commander Heald to stay in the fort, Kinzie ultimately enlisted fellow trader Alexander Robinson, who eventually managed to evacuate some survivors to Grand River and Detroit.
Beaubien, Robinson and Bailly continued to trade during the conflict, supplied by Dickson rather than his American competitors. In January 1814, an American expedition led by Robert Forsyth (John Kinzie's half-brother) captured Bailly and three other traders at St. Joseph. John Kinzie then traveled to St. Joseph, where he convinced several native American leaders to travel to Greenville, Ohio to attend an American peace conference which led to the Treaty of Greenville (1814), although other Native leaders (particularly Main Poc refused)
Jean Baptiste Beaubien