Allen Fredrick Sapp was born on January 2, 1928, on the Red Pheasant Reserve in north central Saskatchewan. A descendant of the great Plains Cree Chief Poundmaker, Sapp was a weak and sickly child whose mother suffered from tuberculosis and died while he was away at residential school. Raised by his maternal grandparents, Albert and Maggie Soonias, he was cared for primarily by his grandmother, with whom he shared a deeply tender relationship that would later inspire some of his most sensitive works. As a child, Sapp was frequently bedridden due to illness and found solace in drawing and painting. At age eight, his grandmother bestowed upon him the Cree name Kiskayetum (he perceives-it). At fourteen, he contracted spinal meningitis and nearly died, but survived to fulfill what his grandmother believed was his purpose.

Sapp never learned to read or write, and his grandfather removed him from the Red Pheasant school to work on the farm. After his grandmother's death in 1963, Sapp moved to North Battleford with his wife and young son to pursue a career as a professional artist. Initially, he painted commercial subjects he believed would appeal to buyers—mountains, streams, and animals he had only seen in pictures—and adopted a more "acceptable" appearance with short hair and horn-rimmed glasses. In 1966, while trying to sell his paintings at a medical clinic, he met Dr. Allan Gonor, a meeting that would transform both their lives. Gonor immediately recognized the depth in Sapp's work and encouraged him to paint what he knew: life on the Red Pheasant Reserve and his own people.

This encouragement opened a creative floodgate. Sapp began painting his childhood memories with extraordinary detail and emotional depth, working from what appeared to be a photographic memory. His unique approach involved no preliminary sketches or photographs—he simply thought deeply about a memory and then began painting, allowing forms and images to emerge on the canvas as if they were already present, waiting to be revealed. His paintings were often rendered from a child's perspective, as he seemed to return mentally to the exact moment he was depicting, whether lying on his grandmother's bed or climbing a tree. With Dr. Gonor's mentorship and connections to art professionals including Wynona Mulcaster at the University of Saskatchewan, Sapp's career rapidly accelerated.

His first major exhibition at the Mendel Art Gallery in Saskatoon in April 1969 drew 13,000 viewers over Easter weekend, with most of the sixty-one works selling on opening night. This success launched exhibitions across Canada, the United States, and London, England. Sapp's work depicted the quiet dignity of Cree life during the Great Depression, capturing family, community, and the intimate connection between his people and the land. Critics praised his ability to create "illusionism so arresting as to constitute a revelation" and noted his extraordinary capacity to infuse his canvases with mood, feeling, and emotion. As his success grew, Sapp reclaimed his Cree identity, growing his hair into long braids tied with deerskin and wearing beaded medallions and a cowboy hat.

Sapp received numerous honors including election to the Royal Canadian Academy of Arts in 1975, the Saskatchewan Award of Merit in 1985, and appointment as an Officer of the Order of Canada in 1987. In 1989, the City of North Battleford opened the Allen Sapp Gallery: The Gonor Collection, making him the only living Canadian artist at that time to have a museum dedicated to his work. He received a Lifetime Award for Excellence in the Arts from the Saskatchewan Arts Board in 1996, an honorary doctorate from the University of Regina in 1998, and the Governor General's Literary Award in 2003 for his illustrations in the children's book "The Song Within My Heart." Allen Sapp died peacefully in his sleep on December 29, 2015, in North Battleford, just days before his 88th birthday.