Virtually all paper and board grades have one or more mechanical property specifications. These are typically fracture properties, but the subfracture mechanical properties are also important. In many situations raw material and papermaking variables impact subfracture and fracture properties in similar and predictable ways. In this review we discuss the impact of fiber and paper machine variables on the mechanical properties of paper and board up to the point of failure. As with any real material, the physical properties (mechanical, optical, electrical, etc.) are not independent but depend upon the constituents and structure of the material. We discuss these connections where appropriate. From a historical perspective, those “turning points” that led us to greater understanding of the mechanical properties are pointed out, as are situations where work is needed.