Some dude named Robert C Baker:

Baker’s innovation was to mold boneless bite-size morsels from ground, skinless chicken (often from the little-used parts of the bird), and encase them in a breading perfectly engineered to solve two key problems: It stayed put through both frying and freezing, critical for mass production and transportation. 

Like all things “American,” chicken nuggets started with World War II:

During World War II, chicken became many Americans’ primary source of protein after the U.S. military commandeered red meat for soldiers, creating a beef shortage at home. The massive chicken demand incentivized businesses to produce the birds more cheaply, says anthropologist Steve Striffler

Read the rest, and I’d be in big trouble without Chicken McNuggets on road trips…