Cortex harbors a diverse range of inhibitory interneuron (IN) types, each of which shapes cortical activity in a unique way. Collectively, these INs control and orchestrate neuronal activity, thereby bestowing cortex with its computational power. Whereas genetic markers have greatly facilitated the study of various cortical IN types, a selective marker for INs in L1 has long been missing. Here, we use the recently identified neuron-derived neurotrophic factor (NDNF) to characterize the properties of mouse auditory cortex L1INs in vitro. First, using in vitro patch-clamp recordings in combination with optogenetics, we study outbound connectivity of NDNF L1INs and find that they broadly control cortical L2/3, including parvalbumin and vasoactive intestinal peptide expressing interneurons. Second, we describe two major electrophysiological clusters within NDNF L1INs and validate and use an intersectional genetic approach to specifically access neuropeptide Y (NPY) expressing NDNF L1INs using in situ hybridization. Employing this approach, we report very similar electrophysiological properties and connectivity patterns of NDNF and NDNF/NPY L1INs. Third, we demonstrate that, after sufficient stimulation, NDNF L1INs are capable of persistent firing, an activity mode which uncouples outputs from current inputs. Persistent firing in these cells comes with a transition into a highly excitable electrophysiological state, which is maintained for the duration of stimulation and reverts only after a protracted period of rest. In conclusion, and in combination with their previously described control of distal pyramidal cell dendrites and long-range innervation, we find that NDNF L1INs mediate top-down control of almost the entirety of superficial cortical circuits.