A system for accessing a surgical target site and related methods, involving an initial distraction system for creating an initial distraction corridor, and an assembly capable of distracting from the initial distraction corridor to a secondary distraction corridor and thereafter sequentially receiving a plurality of retractor blades for retracting from the secondary distraction corridor to thereby create an operative corridor to the surgical target site, both of which may be equipped with one or more electrodes for use in detecting the existence of (and optionally the distance and/or direction to) neural structures before, during, and after the establishment of an operative corridor to a surgical target site.