This lowland marsh area, now known as McNabney Marsh, was first visited by the Bay Miwok's Chupcan people, a local tribelet thought to have consisted of about 200 people. With the vast fishing, hunting, and plant resources of the bay, marshlands, and upland environments, these Native Americans were able to sustain their existence here for centuries. Even though there was no Spanish Mission in the immediate vicinity, their way of living intimately with the land was forever altered in the 1800s with the influx of explorers and missionaries. The construction of a major rail line through the area in the 1880s helped define the marsh as it is seen today. The area was an ideal location for the development of the Peyton Chemical Company and the Mountain Copper Company, both located at the mouth of Peyton Slough, because the town of Martinez offered numerous shipping and rail services. The area of the Preserve with pepper woods and eucalyptus was most likely the site of worker housing for the chemical company located nearby until 1910, and the pepper woods line an old road made of "clinker" stones produced through smelting operations.