What year did McDonald’s launch the Happy Meal nationwide?

When Yolanda Fernández de Cofiño and her husband started the first McDonald's franchise in Guatemala back in 1974, she realized kids were often leaving food unfinished. She launched a "Ronald Menu" with smaller portions, and the corporate offices in the U.S. eventually took note. They tasked marketing executive Bob Bernstein to further develop the idea and get it ready for a U.S. rollout. He eventually settled on the Happy Meal branding, and after successful tests in 1977, McDonald's made it available to children across the country (and most of the world) in 1979. Fernández was awarded a second Ronald Award for her contribution (her first was for the idea to celebrate birthdays in-store), and Bernstein was awarded a solid bronze Happy Meal box.