Big Bear (Mistahimaskwa) was born around 1825 near Jackfish Lake, north of present-day North Battleford. His father, Black Powder (an Ojibwa) was the Chief of a small mixed band of Cree and Ojibwa. His Mother was a Cree woman.

Big Bear established himself as a leader in the late 1850s and early 1860s. In 1871 he was the leading chief of the Prairie River People and by 1874, headed a camp of 65 lodges (approximately 520 people). His influence rose steadily in the following years, reaching its height in the late 1870s and early 1880s.

During the 1880s was the time when the Canadian government in Ottawa was attempting to deal with the Aboriginal people within her territory. The Aboriginal people were being forced onto reserves and hasty negotiations to sign treaties giving away their rights were begun. Although he appeared at the negotiations in the territory of Treaty #6, Big Bear refused to sign. Big Bear was the first major chief on the prairies to take a stand against the treaty process. Over the next six years, Big Bear continued to refuse treaty. Finally on December 8, 1882, when his people faced destitution and starvation, Big Bear signed an amendment to the treaty. At this time his following had dwindled to 114 people.

In the late 1870s, Big Bear tried to create a political confederation of Indian bands capable of forcing concessions from the government. From 1878 to 1880 he travelled through the Canadian Northwest and Montana trying to unite the bands. In the 1880s Big Bear's efforts focused on uniting Cree bands and attempting to create an Indian territory in the Northwest through adjacent reserves. The government refused to grant contiguous reserves and did not respond to joint meetings with the Cree bands: such as the one organized by Big Bear at Fort Battleford in May 1884 to present their grievances. In June 1884, Big Bear hosted a Thirst Dance at the Poundmaker Reserve. The event, which was attended by over 2000 people, was disrupted by the NWMP and only the efforts of Big Bear and Poundmaker (Pitikwahanapiwiyin) averted violence.

The Canadian government was having difficulty administering the reserve system, it was left to the sole discretion of the appointed Indian Agent to distribute food and other necessities of life. The people living on the reservations were not allowed to travel off the reserves to hunt or fish. The people were starving and freezing to death. Big Bear continued to try negotiation with the government, to no avail. As a result of the government's refusal to negotiate with him, Big Bear began to lose influence over his band's Warrior Society during the winter of 1884-1885. On 2 April 1885, Big Bear's band, led by his son Ayimisis and the war chief, Wandering Spirit (Kapapamahchakwew), killed nine people at Frog Lake. Big Bear's efforts to stop the massacre failed. No longer in control of the band, Big Bear remained in the background counseling peace during the rest of the Northwest resistance. On April 14th, Wandering Spirit moved to attack Fort Pitt. Big Bear successfully negotiated the surrender of the 44 civilian inhabitants and the police evacuation. The band fought General Strange at Frenchman's Butte on March 28th, and again at Loon Lake on June 2rd. Once again, Big Bear did not participate in the fighting on either occasion.

Big Bear surrendered at Fort Carleton on July 2nd. He was brought to trial in Regina on September 11, l885. After deliberating for fifteen minutes, the jury found him guilty of Treason and Felony, and he was sentenced to three years at the Stony Mountain Penitentiary. Released in February 1887 because of poor health, Big Bear settled on the Poundmaker reserve where he died on 17 January 1888.