From the Make Blog:
"On this day in 1765, Eli Whitney, Jr. was born in Westborough, Massachusetts. Whitney would go on, most famously, to invent the cotton gin, which revolutionized cotton production in the antebellum South. He eventually became the most famous early American proponent of interchangeable parts, and also invented one of the world's first milling machines."
Here's the Make Magazine post about Eli Whitney.