This beautiful estuary was home to ancestors of Native Americans as far back as 9,000 years ago, who likely migrated across the Bering Land Bridge. Unfortunately, not much is known about these early inhabitants due to destruction of archaeological sites due to flooding and human activities. As time passed, tribes began to establish themselves, and the main tribes that lived at Bolsa Chica were known as the Tongva and the Acjachemen. They lived in seasonal settlements on the Mesa, using the mild coastal weather to escape the harsh winter conditions in the Santa Ana Mountains, utilizing reed and grass hemispherical huts called wickiups or wigwams, and subsisting on what could be collected from the land. They were accomplished hunters and gatherers and were particularly skilled at creating fine canoes for fishing and traveling to the nearby Catalina Island. Like the early inhabitants, little is known about these tribes, with the exception of a few burial sites, shell deposits, and an archaeological treasure: Cog stones. More than 150 of these mysterious stones have been uncovered at Bolsa Chica. Cog stones are rounded and flattened some may have a singular hole in the center, and may have grooves or carvings around the edges, but they do not show signs of erosion, which could imply they were used for ceremonies or decoration. One theory is that they may have represented astrological bodies such as the sun, moon and stars and were used as a calendar system. Similar artifacts have been found in Peru and Chile – however it is unknown whether any connection exists between the South American and North American locations.