Lakeside is a Census Designated Place (CDP) in San Diego County, California. The population was 20,648 at the 2010 census, up from 19,560 as of the 2000 census. Lakeside began when the land that it is on, near Lindo Lake, was purchased by the El Cajon Valley Land Company in 1886. It started as a resort town, based around the once renowned automobile Race course at Lindo Lake that Barney Oldfield made famous in 1907. It was once home to the historic Lakeside Hotel, a destination for health and relaxation reached by a long Day's buggy ride or by train.