Oceanside is the third largest city in San Diego County, California. The city has a population of 173,303. Together with Vista and Carlsbad, it makes up the Tri-City area. The city is just south of U.S. Marine Corps Base Camp Pendleton, the busiest military base in the United States. Oceanside has grown massively from the 1970 census report of 45,000 people. Much of the city area was developed into single-family home tracts when real estate booms took place in the 1970s and 1980s. Since 1990, more commercial and industrial development to diversify Oceanside's economic base, with another population boom ever since. According to the US census, Oceanside's continual growth will put the city population estimates above the 200,000 mark in 2010 or exceed 250,000 by the year 2020. Oceanside apartments for rent comparison page shows most up to date rent information on Oceanside apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.