invented the odometer on this date in 1847. He invented it during the Mormon migration from Missouri to Utah. He'd been trying to keep track of how far they'd traveled by counting the revolutions of a wagon wheel: 360 revolutions per mile, and he counted them all. But after a few days of that, he got bored. He wrote in his journal: "I walked some this afternoon in company with Orson Pratt and suggested to him the idea of fixing a set of wooden cog wheels to the hub of a wagon wheel, in such order as to tell the exact number of miles we travel each day. He seemed to agree with me that it could be easily done at a trifling expense." A carpenter named Appleton Harmon constructed a device to Clayton's specifications, and Clayton dubbed it the "roadometer." His records of the journey were published in 1848 and proved invaluable to the "Forty-niners" of the Gold Rush the following year.