Marsh Creek State Park, State park in Contra Costa County, United States.

Marsh Creek State Park covers vast lands with varied terrain that includes riparian zones, grasslands, wetlands, and a historic 19th-century house. These different habitats create a diverse landscape where visitors encounter varied plant and animal communities.

The land was long inhabited by indigenous peoples before becoming a settlement point for European arrivals in the early 1800s. A prominent medical doctor established himself there and left behind a house that still stands as a historical landmark.

The creek and park carry the name of John Marsh, the first non-Hispanic European settler in what is now Contra Costa County. Marsh had a four-room adobe built for him by local Miwok people, whom he treated free of charge; the tribesmen built it in return. Excavations have uncovered human remains and burial sites, which park planners intend to protect within the park boundaries.

The park is not yet open to the public, so there are no trails, parking or facilities for visitors. It lies about 3.3 miles (5.3 km) south of downtown Brentwood in east Contra Costa County, beside Marsh Creek Reservoir. The property is fenced and the stone house is still undergoing renovation.

John Marsh had the house's 65-foot observation tower built so he could spot rustlers approaching his ranch. The original stone tower collapsed in the 1868 Hayward earthquake; a wooden replacement fell after the 1906 quake. The house is the earliest substantial building in Contra Costa County not built entirely of adobe.