The source of Rush Creek lies high on Mount Lyell, and its upper forks descend from Marie Lakes and from Davis Lakes on Mount Davis, then combine to flow through Waugh Lake, Gem Lake, Agnew Lake, Silver Lake, and Grant Lake on its way to Mono Lake. After Rush Creek passes through Grant Lake, Parker and Walker Creeks enter it just above the Narrows. The Narrows is a point where steep cliffs rise up from both sides of the stream, and the Rush Creek Bottomlands extend from the Narrows to Mono Lake.