A surgical instrument that includes an elongate channel that is configured to operably support a surgical staple cartridge therein. In at least one form, an anvil is pivotally coupled to a proximal end of the elongate channel such that the anvil is pivotal about a discrete, non-movable anvil axis defined by the elongate channel. A firing member is configured for axial travel within the elongate channel in response to an application of firing motions thereto. The firing member is configured to movably engage the anvil and the elongate channel to space the anvil relative to the elongate channel at a desired spacing as the firing member is axially driven through the elongate channel. A closure member is configured to move the anvil from an open position to closed positions relative to the elongate channel upon application of closure motions to the closure member.