We performed ontogenic, transcriptomic and spatial characterization of sciatic nerve Macs (snMacs). Using multiple fate-mapping systems, we show that snMacs do not derive from the early embryonic precursors colonizing the CNS, but originate primarily from late embryonic precursors and get replaced by bone marrow-derived Macs over time. Using single-cell profiling, we identified a tissue-specific core signature of snMacs and found two spatially-separated snMacs: Relmα + Mgl1 + snMacs in the epineurium and Relmα Mgl1 snMacs in the endoneurium. Globally, snMacs lack most core signature genes of microglia, with only the endoneurial subset expressing a restricted number of these genes. Single-cell transcriptomics revealed that in response to injury both snMacs respond differently and that the PNS, in contrast to the CNS, is permissive to prolonged engraftment of monocyte-derived Macs recruited upon injury.