sentences:  Before the 18th century, the San Juan Creek watershed was mostly Acjachemem Native American territory, which extended from Aliso Creek in the north to San Mateo Creek in the south, a distance of roughly .Most of the population lived along the two major streams in the area, San Juan and San Mateo Creeks, as well as Arroyo Trabuco.The Acjachemem, who numbered roughly 2000 overall, were hunter-gatherers, living in small, semi-permanent villages close to water sources.