Spontaneous action potential discharge (spAP) is both ubiquitous and functionally relevant during neural development. spAP remains a prominent feature of supraspinal networks in maturity, even during unconsciousness. Evidence suggests that spAP persists in mature spinal networks during wakefulness, and one function of spAP in this context could be maintenance of a “ready state” to execute behaviors. The extent to which spAP persists in mature spinal networks during unconsciousness remains unclear, and its function(s), if any, are likewise unresolved. Here, we attempt to reconcile some of the questions and contradictions that emerge from the disintegrated picture of adult spinal spAP currently available. We recorded simultaneously from large populations of spinal interneurons in vivo in male rats, characterizing the spatial distribution of spAP in the lumbar enlargement and identifying subgroups of spontaneously active neurons. We find (1) concurrent spAP throughout the dorsoventral extent of the gray matte...