Los Angeles County, on the northeast by San Bernardino County, on the east by Riverside County, and on the southeast by San Diego County. The northwestern part of the county lies on the coastal plain of the Los Angeles Basin, while the southeastern end rises into the foothills of the Santa Ana Mountains. Most of Orange County's population reside in one of two shallow coastal valleys that lie in the basin, the Santa Ana Valley and the Saddleback Valley. The Santa Ana Mountains lie within the eastern boundaries of the county and of the Cleveland National Forest. The high point is Santiago Peak (), about east of Santa Ana. Santiago Peak and nearby Modjeska Peak, just shorter, form a ridge known as Saddleback, visible from almost everywhere in the county. The Peralta Hills extend westward from the Santa Ana Mountains through the communities of Anaheim Hills, Orange, and ending in Olive. The Loma Ridge is another prominent feature, running parallel to the Santa Ana Mountains through the central part of the county, separated from the taller mountains to the east by Santiago Canyon. The Santa Ana River is the county's principal watercourse, flowing through the middle of the county from northeast to southwest. Its major tributary to the south and east is Santiago Creek. Other watercourses within the county include Aliso Creek, San Juan Creek, and Horsethief Creek. In the North, the San Gabriel River also briefly crosses into Orange County and exits into the Pacific on the Los Angeles-Orange County line between the cities of Long Beach and Seal Beach. Laguna Beach is home to the county's only natural lakes, Laguna Lakes, which are formed by water rising up against an underground fault. Regions of Orange County Orange County is sometimes divided into northern and southern regions. There are significant political, demographic, economic and cultural distinctions between North and South Orange County. A popular dividing line between the two regions is the Costa Mesa Freeway. North Orange County, including Anaheim, Fullerton, Garden Grove and Santa Ana, was the first part of the county to be developed and is culturally closer to neighboring Los Angeles County. This region is more Hispanic (mostly Mexican) and Asian (predominantly Vietnamese and Korean), more densely populated (Santa Ana is the fifth most densely-populated city in the United States with a population of over 200,000), younger, less wealthy and with higher unemployment. It has more