A surgical end effector that includes a first jaw that is configured to operably support a surgical staple cartridge therein and a second jaw. The first and second jaws are supported for selective movement between an open position and a closed position relative to each other. A lock member is movable between an unlocked configuration that corresponds to an open position of the jaws and a locked configuration wherein the lock member prevents a firing member from being moved from a starting position within the end effector unless a surgical staple cartridge that has cam assembly located in an unfired position is supported within the first jaw.
