Legendary country music singer Glen Campbell has died at the age of 81 after a long battle with Alzheimer's. According to a source, Campbell died August 8 around 10 AM in a Nashville facility. With a career spanning over 50 years, Campbell released more than 70 albums with hits including "Gentle on My Mind," "Wichita Lineman," "Galveston," "Country Boy" and his best-selling single, "Rhinestone Cowboy."