Suisun Valley

Topography

Suisun Valley is a region in the California Coast Ranges that is bordered on the east side by the Blue Ridge of the Vaca Mountains, and on the west side by the Howell Mountains, which are also called the St. George Range. The valley is located almost entirely in Solano County with a northern terminus near the Napa County borderline, and a southern terminus at Suisun Bay in the estuary where the Sacramento River enters San Francisco Bay. Elevations on the valley floor range from 100 to 200 feet (30 to 61 m) above sea level, rising steeply to 1,122 feet (342 m) at Okell Hill on the north side, and to 2,162 feet (659 m) on the west side at Twin Sisters, a twin summit that is the high point of the Howell Mountains, as well as a prominent landmark in the valley. Blue Ridge on the east side of the valley exceeds 2,000 feet (610 m) elevation for much of its length. The watershed in Suisun Valley drains southward into the Suisun Bay. In the Vacaville-Dixon area, which lies to the east of Suisun Valley, the watershed drains eastward in to the Sacramento River.