The Merced River drops over Nevada Falls and Vernal Falls, together known as the "Giant Staircase", then receives Illilouette Creek and flows into Yosemite Valley, where it meanders between pine forests and meadows that fill the valley floor. Tenaya, Yosemite, Bridalveil and Pigeon Creeks join the Merced River in Yosemite Valley. Beyond the glacial moraine at the western end of the valley the river flows through the steep Merced River Canyon, picks up Cascade Creek and turns south near El Portal. State Route 140 follows the river out of the west entrance to the national park, a few miles before the South Fork Merced River, the largest tributary, joins from the left.