East Bay Walls
East Bay Walls, also known as the Berkeley Mystery Walls, is a misnomer, as there are many such crude walls throughout the hills surrounding the San Francisco Bay Area. In places, they are up to a meter high and a meter wide and are built without mortar; the walls run in sections anywhere from a few meters to over a half mile long. The rocks used to construct the walls are a variety of sizes. Some are basketball-sized rocks, while others are large sandstone boulders weighing a ton or more. Parts of the wall seem to be just piles of rocks, but in other places it appears the walls were carefully constructed. The exact age of the walls is unknown, but they have an old appearance. Many of the formations have sunk far into the earth, and are often completely overgrown with different plants.
The walls are not continuous and are composed of multiple sections, so they are not fences. They are not tall enough to have been used as defensive barriers. The East Bay Regional Park District simply calls them "rock walls" and notes that they are not mysterious. Livestock, such as cattle, have grazed in the east and south Bay Area hills since the arrival of European settlers. Clearing land of scattered rocks would have eased the ability to move livestock. Placing the rocks into walls would have helped to guide the movement of the animals or to help corral them.
No written documentation exists to identify when they were built, by whom, or why, leading some to consider them to be mysterious.
Some people considered the Ohlone Indians to have been the builders, although they were hunter-gatherers and are not known to have built permanent structures. Some specialists have noted that the walls look similar to structures found in rural Massachusetts, Vermont, and Maine.
In 1904, UC-Berkeley Professor John Fryer suggested that the walls were made by Mongolian Chinese who traveled to California before the Europeans, although there is little evidence for this or for pre-Columbian Chinese influence in America. Forensic geologist Scott Wolter has theorized that the wall is only two to three hundred years old, suggested by the thick weathering rind on the limestone rock he was authorized to sample.
Recent testing of lichen on the rocks suggests that they were probably built between 1850 and 1880, the early American era in California. Settlers might have built the walls using Chinese, Mexican, or Native American laborers, although specifically who built them has not been determined.
The stone walls are accessible in several area parks, including Ed R. Levin County Park  in Santa Clara County and Mission Peak Regional Preserve  in Alameda County, as well as many other parks.
As of 2016, archaeologist Jeffrey Fentress is measuring and mapping the walls to eventually gain protection from development or other destruction. Additional stone walls with unclear origin or purpose occur in other places near the San Francisco Bay, and researchers continue to discover more information about the walls.
- Hervieux, Linda (27 August 2016). "The 'East Bay Walls' Continue to Confound". Newser. Retrieved 17 September 2016.
San Francisco archeologist says there is much to learn from mysterious rock walls
- "Bay Area facts: Berkeley Mystery Walls' origins not so off-the-wall". San Jose Mercury News. Bay Area News Group. 12 August 2016. Retrieved 17 September 2016.
It turns out, they’re not much of a mystery, according to Beverly Ortiz, cultural services coordinator with the East Bay Regional Park District.
- "America Unearthed: Season 3, Episode 7 Marco Polo Discovers America (20 Dec. 2014) TV Episode - 60 min - History". IMDb.com. Amazon. Retrieved 31 December 2014.
- "Stone walls at Ed Levin County Park". 2007-07-11. Retrieved 2013-04-23.
- "East Bay Walls of CA". 2010-10-04. Retrieved 2013-04-23.
- Kimmey, Samantha (24 July 2014). "Mystery rocks draw scholarly investigation". Pt. Reyes Light. Retrieved 17 September 2016.
Historical research ...conducted by Mr. Wing and his two students ... indicates [the wall] was created during the 19th century ranching era.