Southern California's cogged stones represent a great unknown in California prehistory. Their localized range, lack of similarity to anything else, and sheer numbers leave one a bit bewildered as to their purpose.
The modern discovery of cogged stones began sometime in the late 1800s. As fanning expanded in southern California's Orange County, so did archeological discoveries. Originally, it seems, they were largely overlooked. But by the 1930s they had been found in enough quantities in such a small area as to capture some of the public's attention. Beginning with J.W. Winterbourne's Orange County excavations in the late 1930s, followed by Herman Strandt and H. Heizer in the 1940s and 1950s, cogged stones received a great deal more attention. One time State Senator and Mayor of Riverside, Samuel Cary Evans, had a collection of them and compiled a now-lost list of some thirty possible uses of cogged stones, which included stone machinery and oil burners. To this day, there is still much uncertainty about what cogged stones are, though recent ethnographic evidence may offers some clues.
Cogged stones are simply that, cog shaped stones. They come in a great many varieties but are essentially stone discoidals with "ribs" or "cogs" fashioned onto or into their sides. Cogged stones were made from a range of materials including red ochre, steatite, tonolite, rhyolite, diorite, talc schist, calcium carbonate concretions, sandstone, siltstone, limestone, andesite, dactite, dolerite, pumice, basalt, and granite.
Dating cogged stones has been relatively difficult as most have been found in heavily plowed fields. Only a few of those found in situ are datable. Known dates and estimates place their appearance during the Early Milling Stone Horizon, some 7,500 years ago. Some 2,500 years later they disappear abruptly. Their range is centered along the Santa Ana River drainage in southern California's Orange and Riverside Counties. This extremely small geographic area contributes to their peculiarity. Though limited in range, some sites, like Bolsa Chica in Orange County, have revealed over 1,000 cogged stones in a few acres. On occasion, they have been found some distance from the Santa Ana River, known from isolated examples in Ventura and Los Angeles Counties, and as far east as Chandler, in south central Arizona. It is uncertain if the isolated cogged stones are from the Santa Ana River basin as well, but many of the known examples are made of comparable rock types. This being said, it is believed that the migration of the cogged stones shows cultural affiliation between these areas—an affiliation which is difficult to accurately know, compare, or state because we don't know who those people were. Historically, the Gabrieliiio, Luisa°, and Cahuilla occupied the areas in which cogged stones are most commonly found, but they are part of the Uto-Aztecan linguistic group, a group which entered California roughly at the same time cogged stones disappear from the archeological record. It is therefore highly unlikely that their culture is responsible for cogged stones.
As of now, there is no single answer as to what cogged stones were made for. Some of the earliest ideas put forth were based on the presumption that they were utilitarian objects such as net weights, oil burners, nut grinders, mace heads, or cogs for stone machines. We now believe with some certainty that they were not utilitarian.
The current view holds them to be ceremonial objects, but their meaning and symbolism are open for debate. One of the earliest ideas was that they represented sea life. From this perspective, some represent starfish, others represent fish vertebrae, while others imply jellyfish. If you visit the Bowers Museum in Orange County, you will see a convincing display of this. However, it does not explain ovoid or clover forms or the drastic range in the number of individual cogs. Another view is that cogged stones may represent notable stars in the night sky, but there is little to back this view at the moment
The actual events that created the Cogged Stone culture, and what caused their abrupt end, what they symbolized, and who made them, will likely never be satisfactorily answered. However, it is possible to take the information at hand and interpret it with your best guess. In essence, they were a pillar of a long gone culture. Likely ceremonial and symbolic in nature, they held a strong significance to a people we will never know. Important enough to be created and replicated for over two millennia, we are still unable to definitely determine the purpose of these cogged stones.
