The Boss 302 was created in 1969 by Ford to combat the new Camaro and Firebird from Chevrolet and Pontiac. The Mustang was outperformed by the Camaro, which was introduced in 1967, so a higher trim level with more power and handling had to be created to combat this new competitor.
Ironically, the construction of the 69-70 Mustang fastbacks was heavily influenced by the same team who designed the first generation Camaro, brought to Ford when Semon Knudsen of Pontiac became president of Ford Motor Company in 1968. The Boss name is due to the head designer giving Knudson the nickname of "Boss." It sounded like a good name for the Mustang intended to overthrow the Camaro in the muscle car segment, so it stuck.
