Bethel Island

Franks Tract State Recreation Area (SRA) is a state park unit of California, United States, featuring a flooded area in the Sacramento–San Joaquin River Delta. It is accessible only by water. Franks Tract, and a smaller adjoining submerged property called "Little Franks Tract", are situated between the False River and Bethel Island. The recreation area is used primarily for fishing and waterfowl hunting, because of its exposure to frequent strong winds and fluctuating water levels. In times of high water, the entire site can be submerged except for portions of the old levees. The 3,523-acre (1,426 ha) park was established in 1959. It is managed from nearby Brannan Island State Recreation Area, 6 miles (9.7 km) to the northwest.

{{Merger with Franks Tract State Recreation Area has been proposed. Please see Talk page.}} The Antioch Bombing Target a 500-acre (200 ha) plot was a United States Navy target used from 1943 to 1952. It is now part of the Franks Tract State Recreation Area.

Jersey Island is an island in the Sacramento-San Joaquin River Delta of Contra Costa County, California, approximately 10 kilometres (6.2 mi) east of Antioch. The 1,425-hectare (3,520-acre) bounded on the west by the San Joaquin River-Stockton Deepwater Shipping Channel, on the north by the False River, on the northeast by Piper Slough, on the east by Taylor Slough, and on the south by Dutch Slough. It is administered by Reclamation District 830.

Marsh Creek is a stream in east Contra Costa County, California in Northern California which rises on the eastern side of Mount Diablo and flows 30 miles (48 km) to the Sacramento–San Joaquin River Delta at Oakley, California, near Big Break Regional Shoreline. The creek flows through Marsh Creek State Park (California), where water is impounded to form Marsh Creek Reservoir, then through the city of Brentwood, California.

The Holland Tract is an island in the Sacramento–San Joaquin River Delta. It is part of Contra Costa County, California, and managed by Reclamation District 2025. Its coordinates are 37°59′55″N 121°36′08″W, and the United States Geological Survey measured its elevation as 7 ft (2.1 m) in 1981. It appears on a 1952 United States Geological Survey map of the area.

Bradford Island is a 2,172-acre (879 ha) island of the Sacramento–San Joaquin River Delta, in Contra Costa County, California, United States. Bradford Island is inaccessible by roads, and is served by a ferry across the False River from nearby Jersey Island. Approximately 48 people lived on the island as of 2020; other uses of land include wheat farming, cattle grazing, and natural gas extraction. Bradford Island is a reclaimed peat wetland; as it lies below sea level, it is protected by flooding by levees. These, as well as a pump station and internal drainage canals, are administered by Reclamation District 2059, founded in 1921. The levees have been breached on several occasions, leading to the island becoming flooded. Bradford Island is one of eight Delta islands considered critical to the region's water quality by the California Department of Water Resources.

Knightsen is a census-designated place (CDP) in Contra Costa County, California, in the United States. As of the 2010 census, the CDP population was 1,568, up from 861 reported in the 2000 census.

Quimby Island is a small island in the Sacramento–San Joaquin River Delta, whose coordinates are 38.0251993°N 121.5713413°W / 38.0251993; -121.5713413 (Quimby Island). It is in Contra Costa County, and managed by Reclamation District 2090.

Rhode Island is a small, partially submerged island in the San Joaquin River delta, in California. It is part of Contra Costa County. Its coordinates are 37.9996445°N 121.5752300°W / 37.9996445; -121.5752300 (Rhode Island). It appears on a 1952 United States Geological Survey map of the area.

Little Mandeville Island is a small, mostly submerged island in the San Joaquin River delta, in California. It is part of San Joaquin County, and its coordinates are 38.0104776°N 121.5649522°W / 38.0104776; -121.5649522 (Little Mandeville Island). In 1994, 376 acres (152 ha) of former farmland was inundated with water after a levee broke.

Oakley is a city in Contra Costa County, California, United States. It is within the nine-county San Francisco Bay Area. The population at the 2020 United States census was 43,357. Oakley was incorporated in 1999, making it the newest incorporated city in Contra Costa County.

Sand Hill is a former unincorporated community now annexed to Oakley in Contra Costa County, California. It lies at an elevation of 43 feet (13 m). It is west of Knightsten on the far edge of the county.