"In Li'l Abner, Sadie Hawkins was the daughter of one of Dogpatch's earliest settlers, Hekzebiah Hawkins. The "homeliest gal in all them hills", she grew frantic waiting for suitors to come a-courtin'. When she reached the age of 35, still a spinster, her father was even more frantic—about Sadie living at home for the rest of her life. In desperation, he called together all the unmarried men of Dogpatch and declared it "Sadie Hawkins Day". Specifically, a foot race was decreed, with Sadie in hot pursuit of the town's eligible bachelors—and matrimony as the consequence.
"When ah fires [my gun], all o' yo' kin start a-runnin! When ah fires agin—after givin' yo' a fair start—Sadie starts a runnin'. Th' one she ketches'll be her husbin." The town spinsters decided that this was such a good idea, they made Sadie Hawkins Day a mandatory yearly event, much to the chagrin of Dogpatch bachelors. In the satirical spirit that drove the strip, many sequences revolved around the dreaded Sadie Hawkins Day race. If a woman caught a bachelor and dragged him, kicking and screaming, across the finish line before sundown—by law he had to marry her.
Sadie Hawkins Day was first mentioned in the November 15, 1937 Li'l Abner daily strip."
~Wikipedia