It was during the 1960s that Warhol began to make paintings of iconic American objects such as dollar bills, mushroom clouds, electric chairs, Campbell's Soup Cans, Coca-Cola bottles, celebrities such as Marilyn Monroe, Elvis Presley, Marlon Brando, Troy Donahue, Muhammad Ali, and Elizabeth Taylor, as well as newspaper headlines or photographs of police dogs attacking African-American protesters during the Birmingham campaign in the civil rights movement. During these years, he founded his studio, "The Factory" and gathered about him a wide range of artists, writers, musicians, and underground celebrities. His work became popular and controversial. Warhol had this to say about Coca-Cola: