Despite its name, it does not serve the northernmost stations on the network, though it does serve the southernmost station, Morden, as well as 16 of the system's 29 stations south of the River Thames.
På trods af sit navn betjener Northern line ikke de nordligste stationer i netværket, men derimod den sydligste station (Morden Station) og standser på 16 af systemets 29 stationer syd for Themsen.