The Napa River, approximately 55 miles (89 km) long, is a river in the U.S. state of California. It drains a famous wine-growing region, called the Napa Valley, in the mountains northeast of San Francisco. Milliken Creek and Mt. Veeder watersheds are a few of its many tributaries. The mouth is at Vallejo where the inter-tidal zone of fresh and salt waters flow into the Carquinez Straits on San Pablo Bay.