Abstract: There is disclosed an irradiated cortical bone sheet allograft. In an embodiment, the allograft includes a unitary sheet of at least partially demineralized, irradiated cortical bone having a thickness, a width, and a length. The thickness of the unitary sheet of irradiated cortical bone is less the width and the length. In another embodiment, a method of forming the allograft includes obtaining a natural bone from a donor different than a recipient. The natural bone contains a layer of a cortical bone. The method includes cleaning the natural bone to produce a unitary sheet of cortical bone. The method includes at least partially demineralizing the unitary sheet of cortical bone. The method includes freezing the unitary into a frozen state within a sealed package. The method includes irradiating the unitary sheet in the frozen state within the sealed package to sterilize the cortical bone and produce the irradiated cortical bone sheet for implantation in the recipient other than the donor.