Reduced considerably in size, the Stanislaus River leaves the foothills and enters agricultural Stanislaus County at the historic Gold Rush town of Knights Ferry. It is paralleled by State Route 120 as it flows west into the Central Valley, through Oakdale, the largest town on the river, and along the northern edge of the Modesto metro area. At Riverbank it begins to form the border of Stanislaus County (south) and San Joaquin County (north). At Ripon, it is crossed by Highway 99. Below Ripon the Stanislaus flows west-southwest through a low-lying area known as River Junction and past Caswell Memorial State Park. It joins the San Joaquin River at a point about northeast of Vernalis and south of Manteca, upstream (south) of the larger river's mouth at Suisun Bay.