Angle of Repose is a 1971 novel by Wallace Stegner about a wheelchair-using historian, Lyman Ward, who has lost connection with his son and living family and decides to write about his frontier-era grandparents. It won the Pulitzer Prize for Fiction in 1972. The novel is directly based on the letters of Mary Hallock Foote, later published as A Victorian Gentlewoman in the Far West.

The angle of repose or the critical angle of repose, of a granular material is the steepest angle of descent or dip  relative to the horizontal plane to which a material can be piled without slumping. At this angle, the material on the slope face is on the verge of sliding. The angle of repose can range from 0° to 90°. Smooth, rounded sand grains cannot be piled as steeply as can rough, interlocking sands. If a small amount of water is able to bridge the gaps between particles, electrostatic attraction of the water to mineral surfaces will increase soil strength. When bulk granular materials are poured onto a horizontal surface, a conical pile will form. The internal angle between the surface of the pile and the horizontal surface is known as the angle of repose and is related to the density, surface area and shapes of the particles, and the coefficient of friction of the material. However, a 2011 study shows that the angle of repose is also gravity-dependent. Material with a low angle of repose forms flatter piles than material with a high angle of repose.