A surgical stapling instrument, comprising: an end effector, comprising: a first jaw comprising a distal jaw end; and a second jaw movable relative to said first jaw between an open position and a closed position; a firing assembly movable toward said distal jaw end during a firing stroke, wherein said firing assembly comprises: a firing rod; and a lockout bar, a staple cartridge loadable into said end effector, wherein said staple cartridge comprises: a cartridge body; a plurality of staples removably stored in said cartridge body; and a sled movable between a proximal unfired position and a distal fired position to eject said staples from said cartridge body during said firing stroke characterized in that said lockout bar is movable between a distal locked position and a proximal unlocked position relative to said firing rod; wherein the surgical stapling instrument further comprises a lock, wherein said lock is engaged with said firing rod prior to said firing stroke when said lockout bar is in said distal locked position, and wherein said lock is disengaged from said firing rod prior to said firing stroke when said lockout bar is in said proximal unlocked position; wherein said sled is configured to push said lockout bar into said proximal unlocked position when said staple cartridge is loaded into said end effector and said sled is in said proximal unfired position, thereby disengaging said lock from said firing rod. an end effector, comprising: a first jaw comprising a distal jaw end; and a second jaw movable relative to said first jaw between an open position and a closed position; a first jaw comprising a distal jaw end; and a second jaw movable relative to said first jaw between an open position and a closed position; a firing assembly movable toward said distal jaw end during a firing stroke, wherein said firing assembly comprises: a firing rod; and a lockout bar, a firing rod; and a lockout bar, a staple cartridge loadable into said end effector, wherein said staple cartridge comprises: a cartridge body; a plurality of staples removably stored in said cartridge body; and a sled movable between a proximal unfired position and a distal fired position to eject said staples from said cartridge body during said firing stroke a cartridge body; a plurality of staples removably stored in said cartridge body; and a sled movable between a proximal unfired position and a distal fired position to eject said staples from said cartridge body during said firing stroke characterized in that said lockout bar is movable between a distal locked position and a proximal unlocked position relative to said firing rod; wherein the surgical stapling instrument further comprises a lock, wherein said lock is engaged with said firing rod prior to said firing stroke when said lockout bar is in said distal locked position, and wherein said lock is disengaged from said firing rod prior to said firing stroke when said lockout bar is in said proximal unlocked position; wherein said sled is configured to push said lockout bar into said proximal unlocked position when said staple cartridge is loaded into said end effector and said sled is in said proximal unfired position, thereby disengaging said lock from said firing rod.