Once upon a time, a rich wetland flourished, nurtured by the tidal waters of San Francisco Bay. Sunrise crowned the glistening shoreline of a pristine channel of water that came to be known as Yosemite Slough. The word Yosemite originates from the native Miwok word for grizzly bear. Yosemite Slough was a marshland, a nesting area for migrating birds along the Pacific Flyway and a sanctuary for endangered mammals. … Yosemite Slough originated in the lakes of McLaren Park streaming east through the Portola and Bayview Districts to enter San Francisco Bay. This is called a watershed.