A cable backplane system includes a backplane having a plurality of openings and mounting blocks proximate the openings. A cable rack is coupled to a rear of the backplane that includes a tray, spacers coupled to the tray and cable connector assemblies held by corresponding spacers. Each cable connector assembly has a plurality of cables extending between cable connectors. The cable connectors are received in corresponding openings and held in position relative to the backplane by the spacers. Locking assemblies are held by the tray and have a latch proximate to a front edge of the tray configured to interact with a corresponding one of the mounting blocks to lockably couple the tray to the backplane. The locking assemblies each have an actuator at a rear of the tray that is actuated by an installer to lock and unlock the latch with the mounting block.