Glendale is a city in St. Louis County, Missouri, United States. The population was 5,925 at the 2010 census. Glendale was voted the be…Glendale is a city in St. Louis County, Missouri, United States. The population was 5,925 at the 2010 census. Glendale was voted the best place to live in Missouri in 2014 by movoto.com, and was named after the scenic dales or glens in the region.